Mum has denied DSis’s disability her whole life - I don’t know how to deal with it anymore

But how CAN she "stand in the way"? Dsis doesn't live with her; she has no power or authority here; she isn't even going to know anything that you two don't tell her. The alternative to "being firm" is to just stop involving her in these discussions at all. You (plural) don't need her permission or approval to get Dsis what she needs; stop asking for it. Just help Dsis with the practicalities and support her emotionally and remind her, when necessary, that she's getting medical treatment for a medical condition and no, she's not being difficult or a nuisance at all, and if DM ever suggests otherwise, she should probably tell DM what she can do with her suggestions (or just change subject, or realize she's running late and has to go, or whatever works for her). Do things first and let DM find out naturally later (quite a lot later, if that's how things naturally pan out). Let her find out that Dsis has been having a regular physio appointment for months now or that she got crutches or whatever; just be both entirely factual and entirely unapologetic about the fact that X is happening and that you helped organize it. If she questions why she wasn't told, tell the truth: "Because it's tough discussing a disability in any sensible or productive way with someone who denies it exists". Or "Because it makes Dsis feel like shit when you call her lazy for having an illness, and she doesn't need that and neither do I". Or "What for? You never tried to help Dsis with any of this stuff when she's a child - I'm not holding my breath for anything to change now". Don't apologize, don't explain, don't ask for permission or forgiveness. Just support Dsis (who is lucky to have you) and leave DM out of it.

Don't ask questions, either. You've had all the answer you're going to: she did what she did because she didn't want Dsis to be treated differently. It's not a good or a valid reason, but it is the reason - she's not going to change her answer, and she's probably never going to say she's sorry.

And try to remember that Dsis's disability is physical, not intellectual, and it's not your job to manage her relationship with her DM. Maybe if you can show her that it's perfectly possible to make arrangements / decisions without discussing them with DM first, and that you don't have to ask for (or even want) her approval, it'll rub off on her and she'll gradually start feeling able to take the same attitude. But that's down to her. You can help her with the practical stuff; you can't fix the fact the she drew the short straw of mothers. Focus on helping her with what you can, and leave the rest to her.

Yes there are two approaches which would help: practical help now for your sister, regardless of your M’s opinions, and some individual therapy for you and your sister to process the past.

Your mother is no longer an actor in this in the present and the solutions are outside of her.

DM was very much of the mindset that if ignore something, it goes away.

I suspect it was more "There is no way I gave birth to a disabled child"

I’m a bit confused here. Your DSis is 30, does not live with your DM but is struggling because your DM didn’t acknowledge her disability? On the other hand, she was diagnosed as a toddler and had lots of medical support throughout her childhood. So who arranged the diagnosis? Who took her to all the appointments? And why are you getting involved with the issue now?
Maybe your DSis would benefit from some therapy to address any childhood issues she may have, but as far as your DM preventing her from receiving any support now, how would that be the case?

It’s clear from your mum’s initial responses she isn’t in the right place to reflect and recognise what she could have done differently so don’t invest anymore time or energy in trying to make her see sense. Invest it in supporting and encouraging your sister instead.

My mum was told I could be deaf when I was little. I have a lifelong condition that impacts my hearing and can only be temporarily fixed by surgery, I wear hearing aids when the surgery fails. My mum allowed the surgery but no other support and now says I’m “not properly disabled”.

She now uses the fact I’m not permanently deaf as an example of how experts don’t really know what they’re doing and actively advises my brother not to engage with referrals for his children. It’s very difficult but I just ignore her, she isn’t open to hearing the facts.

That is terrible.
I remember watching the short film The Silent Child about a deaf little girl living with a hearing family who refuse to learn sign language. The scene that sticks in my head is her watching all her family chatting around the dinner table but having no idea what their saying or any way of joining in.

Wow! You both need to stop seeing your DM as a good person. She’s belittled your DSIS, ruined her childhood and neglected her medical needs. That’s abuse! I don’t buy the old ‘attitudes were different then’ as if she’s mid-30s, she must have been born around 1990. By then, there was at least some understanding of additional needs. Kids in my high school class in 1992 had 121 helpers. I can time/date this as one assistant was my neighbour, it’s not based on a hazy memory.

It happened but it was NOT normal!

@sergkuchkin what was the diagnosis she was originally given?

Many disabilities have supportive organisations/peer groups that offer programming, supportive groups, counselling etc. It may help your sister understand her disability better.

Definitely reach out to the GP and adult services too.

As for you Mum, times were so different, there was so much shame and worry about females being 'left on the shelf'. In my health care career I've heard thousands of older people and people in more modern times with different backgrounds say this. While I'm not excusing your Mum, it is hard to put what we know in this time and culture to what was present back then. Good examples of this can be found on Call The Midwife - that immense worry about fitting in and sadly the immense ignorance in the community too.

Best wishes to you & your sister (and your Mum too).

I’ve seen this happen within the deaf
community where a relative was never encouraged to learn to sign in the hope that they’d learn to lip read instead. It was an awful experiment and that relative had a very isolated childhood.
All in the past now thankfully but it sounds like you’re giving the support your sister needs now.
Edited to add - it was the school who insisted no-one signed at home or at school, not the family who would have learned had that been the recommendation.

I’ve tried gently bringing it up with DM, but she either shuts down the conversation or gets huffy and starts on about how she “did her best” and “didn’t want DSis treated differently.”

So she's capable of admitting she made mistakes when DSis was younger but still continues to make her feel like shit for needing help now?!

That's outrageous and she needs telling so.

I'd be putting all my support and care into Dsis and going low contact with Mum until she makes apologies and starts getting on board with fully supporting her child.

Honestly I'm probably a similar age to your Mum & I can't fathom her attitude at all.

Things are always changing but to me refusing available help & making a child's life more difficult is hard to understand.

I agree with pps that you need to forget your mum & concentrate on helping your sister to get help now & come to terms with how badly she was let down.

Quite honestly I wouldn’t have kept quiet this long.

I would tell her what an awful parent she was and still is and that she made Dsis’s life harder.

I wouldn't normally advocate for this route, but… assuming that you and your sister

• have no chance of convincing your DM that she (presumably unintentionally) hurt and damaged her own daughter (extremely unlikely — our minds protect themselves against accepting these kinds of things)
• don't want to cut your DM off
• won't be able to, or won't want to, hide the things your sister wants to start doing to accommodate her disability
• don't want to make your DM feel guilty, and
• don't want constant friction between you/your sister and her,

I honestly think that (depending on the nature of the disability) the only practicable route might be to effectively lie to your DM about the impact of her past actions— or, perhaps a nicer way to say it is to frame things in a way that your DM might accept.

You and your sister would absolutely have to be on the same page about this in advance, otherwise your sister would likely feel that you're letting her down, trying to gaslight her and rewrite her own history and reality, and siding against her with your DM. She might even feel betrayed by you raising the possibility of pretending to your DM that her actions were less damaging than they really were — only you know how your sister would be likely to react to such a suggestion.

But if you were both to agree that protecting the relationship could be valuable enough to make it worth cushioning your DM from the truth, you could try to find ways to suggest that needing help now doesn't necessarily mean your DM did the wrong thing to withhold help then. Like, claiming that as your sister gets older, things that her young healthy body might have compensated for in the past are getting more difficult to work around. That kind of lie.

It means your sister (and to some extent you) taking the distress onto herself and keeping it private from your DM, and finding a way to manage and process the feelings she has about both the original issue, and about carrying the ongoing burden of hiding her feelings and her reality — all in order to spare your DM's feelings and maintain the relationship. Which is extremely unfair, since your DM is the one who's responsible for the distress in the first place. But pragmatically, given everything else you've said, I can't think of another way to go forward without the kind of ongoing discord or relationship rupture that I think you've said you and your sister don't want.

I know this is a shitty answer and I feel bad typing it — I hope you do find a better solution.

I have a medication induced neurological involuntary movement disorder called tardive dyskinesia that was caused by some prescribed off label antipsychotic after a head injury. My DM isn't that empathetic about it at times, and I often wonder if it's a general thing either with her generation (laged late 70s), or just that she's not going to accept her daughter is permanently harmed.

I've also had a high frequency hearing loss all my life, which she has been ok about but the lack of anything acknowledged as much as I'd like about my movement disorder hurts sometimes.

Maybe people who don't have the misfortune of health issues aren't really able to be as understanding of those who have them.

I know that is a great sweeping statement and I'm sure it doesn't apply to every loved one of those with disabilities, but it's hard to say anything to my DM because of it I feel quite alone.

You sound a wonderful sister and great loving support. I agree with PPs about leaving your DM out of things.

How is she standing in your sisters way now though?

Your mother is irrelevant now. She's made herself irrelevant.

Concentrate upon helping your sister own her condition, get help to live as an adult with this disability/condition and leave your mother to her idiocy.

This is not good advice. The Mum doesn’t want to acknowledge it. Forcing counselling and a reality she doesn’t want to face is not going to work. That’s not how counselling works either.

OK @sergkuchkin I am going to be painfully blunt, you cannot change what happened to your sister growing up but you can help to change her future and make life more comfortable going forward.

I still see in schools, parents who are reluctant to label a child, lest it follow them for life and they do not realise that it is not an indictment on them or their parenting skill but it can be the key to unlocking help for them.

It was normal in the 70’s and 80’s when I was a kid. If the sister is mid 30’s then she would be born in 85 ish? I remember relatives about that time fighting against an autism diagnosis because they wanted him to stay in mainstream school and get a standard education. The autism label then meant special school and “life skills” rather than GCSE’s. It was also a time when there were programmes in the us and other places claiming to “cure” autism.

i didn’t get a home computer until the early 90’s so there’d have been no google to inform yourself.

yes the mum did things wrong but probably with the best intentions. I don’t think there’s any point beating her up about it now. We’ve all fucked up as parents- but all we can do is make the best decision with the information we have at the time. All it will do is destroy the mother and the sister will be in exactly the same position. Time to move on.

I remember a pupil not getting the support he needed for high-functioning autism. I raised the issue when he arrived in Year 3, although he was not in my form. ( I am told that CBT could have helped, but past a certain stage, patterns of behaviour are too ingrained, but I'm no expert!) He was clearly finding social interaction stressful, and I'm sorry to say that some of his less kindly classmates would wind him up as a sure-fire entertainment, plus a break from humdrum lesson time.
I retired before he left the Junior School, but on return visits, I heard the end of the story.
After one meltdown too many, crisis point was reached, and the parents reluctantly admitted that he had arrived with a diagnosis already made. His parents did not wish him to be singled out or labelled, so "let him be treated just like everybody else".
The staff had experience of supporting "quirky" individuals, and were open to following specialist advice.
He finally flunked out of the Senior School, following the consequences of a heavy cannabis habit. As I said to my former colleagues, the poor little b***r had been blunting the edges, and self-medicating.
Denying a diagnosis will not make the condition go away.

💯 @Allergictoironing . This was my dad who probably was on the autistic spectrum himself, and his attitude to my brother, who has now been diagnosed in his 50s. Sadly he has inherited our father’s ableism and just wants to be “ normal” and not engage with any diagnosis even though it could help him understand himself and access help. It’s such a mess and I resent my late father for it.

You say you do not wat your mother to feel ''guilty'' but she is guilty - very guilty. She was stupid and very negligent regarding your DS health. She needs to see the error of her ways and make amends asap.
As far as people saying she behaved normally for those days - completely untrue - we are not going back to 1930s/40s here..

Does DM have to be closely involved at this stage of Dsis's life? It sounds as if she was not helpful when help was urgently needed, but that's in the past now and the most important thing is for Dsis to get the facilities she needs to function better. Could she not just go ahead and look for what she needs and ignore DM's take on it? As in, 'Thanks for your comments Mum, but I need to get some professional help now and I'm grown up so please leave me to it.'

There must be records, you said there were physios and OTs involved, her doctor must have records of it all. Beside that if you become disabled as an adult you can still get help when there is no history of lifelong problems. My husband is disabled but it happened in his 40s no one has ever suggested that because he was a healthy child he can't get help now so I wouldn't worry about that.