AIBU to feel stuck managing conflict between my two daughters with one really pushing buttons

I also have a teen awaiting ADHD assessment. She wet through a phase of being highly anxious, refusing to eat, and generally being really nasty.
I gambled and pointed out that having ADHD wasn't an issue and she was entitled to, and relieved a lot of accommodations around that. I understood that some things were more difficult for her however having an ND diagnosis was not a license to be a dick and hurt the people who loved her the most. I also pointed out that the adult world would be less accommodating and we would help her develop strategies but not if she was going to be hateful and nasty to me. She could filter and behave to the adults in her extra curriculars and most of the teachers in school. She could therefore manage civil interactions with me, particularly if she wanted lifts, money etc.
A week or so later I realised she was much calmer and being much less argumentative. It landed much better than I expected.
However, in this house it's a regular discussion point. I work with ND kids and accommodate their needs but entitled behaviour crosses a line and the fun stops.

Having had a time when I really didn't get on with a sibling

Please do not try and make them friends. Accept that currently there is no chance. The more you try and push this, the harder they will fight - and feel it's the other one's fault because of their behaviour and that you do not understand how hard it is for them.

The best thing you can do is give them each space. Don't tiptoe round dd1 because you're afraid of her reaction. If dd2 doesn't want her at something of her own, that's fine too. If it's a family thing, then, no, it isn't an option.

I get on well with my sibling now. But over 200 miles apart has helped a lot.

'I am going to adopt some of the advice I’ve got on here to try and minimise family conflict and push DD to adopt a more rational and grown up approach'

Others may disagree but I don't think the aim is to minimise conflict here... Boundaries are likely to increase it, short term at least. Your aim is to let older DD know what is ok and not ok to do in your house, and to step back from managing the relationship between both daughters. If the younger sibling does not wish to engage due to sister's behaviour, you cannot force her to. Yes it's sad, but actually healthy for her imho.

DD1…. Does she have any friends? Ever had a partner?

Palming this problem off to the youngest daughter to correct is emotional bullying.

DD2 is staying out the way and rightly so. She shouldn’t have to deal with any of this. This is purely DD1 and her parents issues to navigate.

From personal experience, 100% correct.

With all kindness OP, you need to stop prioritizing the needs of the entitled 18year old at the expense of her younger sister, ND or not. You're enabling her unkind behaviour.

There is absolutely nothing you can do now to improve their relationship, however hurtful it feels. They will need - or not - find their own way, without your help.

Hey
Iv read she been on adhd meds and now anti anxiety
Can I suggest a combo meds to look at through personal experience in our family. We had success with none stimulant called guafacine (take it in evening) and then elvanse (stim) in morning. It has really helped regulate the anger and behaviour.

Also get your dd2 into therapy to help her deal with her sister and keep communication open with you

Hi agree. I’m a MH Nurse & I’ve supported so many siblings of autistic siblings whom grow up traumatised & resentful that their whole childhood was spent being the reciprecant of awful behaviour & often aggression. Whilst the parents spent the majority of their time & efforts on the ASD / child with challenging behaviours. Most of these siblings all left the family home as soon as they could & avoid spending time with their family as adults

My Mother forced the relationship between us siblings and gave excuses.

One sister has been badly behaved for years, not ND just nasty, She had done a lot of things the worst was running off with our older sisters DH and attempting to seduce mine.

When our Mother died we just had polite conversations at the funeral, none of us have seen her since, it’s been 8 years . No announcements or arguments. Our Mother was her greatest champion because deep down she knew youngest sis was awful. She very probably is mentally ill with something but she has pulled so much over the years it’s exhausting.

Our Mother's excuses for the youngest made the situation worse. I know it’s a totally different kind of behaviour but she could do anything she wanted.

18 - so old enough to move out. Neurodivergent or not (I’m ND, as is my daughter), I cannot imagine a world where I allow my daughter to speak to me, and get away with speaking to me like this. She wants to act like this, and believe this, she can do it away from me. Can’t be doing with putting up with that crap.

What jumped at me from your post OP, the way you justify DD1s horribleness - saying that she "had a point" calling her sister names, just because her sister didnt want her present somewhere.
If I had a relative behaving the way your DD2 does, no way in hell I'd want them anywhere in public with me!
Your poor DD2, she's had to cope with so much! And your attitude certainly doesnt help. Unfortunately unless you tell your 18 y/o she needs to move out (and follow through, once she's finished school), this will just carry on and likely get worse. She is super entitled and doesnt give a shit about others.

Couldn’t have put it better myself !!

Absolute bullshit. This is not discrimination - she would need to be ignoring her sister specifically because she’s neurodiverse. Which is clearly not the case and would be unprovable anyway. And defending yourself against the behaviour of someone who has a disability and who is abusing you, is not ableist bullying. This is not how the Equality Act works. It’s there to protect against actual discrimination and ableist bullying, not to be manipulated in disputes between family members.

I wonder if you could be more unhelpful

Thank you @BertieBotts i will look those up :)

My 11 year old has just been shouting at me about some nonsense and I managed to say “I can help you when you’re calm” rather than trying to jump in and fix the problem, which I was quite proud of, thank you for such detailed advice.

Oh, sorry!! When DS1 (similar age to OP's DD) was little they were in such common use on here that I thought OP would know, but I should have written it in full :)

How To Talk So Kids Will Listen and Listen So Kids Will Talk.

Ideally the original 80s series including the original (with above title) and Teens version, rather than the newer set written by the original author's daughter. The newer set (inc Little Kids, and HTT when Kids Don't Listen) are also good, but the original 80s ones are absolute classics and really clear about how to validate feelings and show empathy without getting involved in fixing or shaming feelings, which is the specific part I was recommending. The later reprints have some good clarifying Q&A as an appendix which is also really great. (It's my favourite parenting book ever so I have owned various copies).

Ffs.. 🤦🏼‍♀️🤦🏼‍♀️🤦🏼‍♀️

Where is any evidence that the younger sister bullying the older one?
DD2 is ignoring DD1 based on her character and past treatment, not based on diagnosis. And if you read the OP properly, you will see that it was indeed DD1 who was ignoring DD2 since she was 11 years old.

You absolutely cannot go to prison for choosing not to interact socially with somebody who is nasty to you, stop posting such total bollocks.

You need to get a grip of yourself. The eldest ignored her sister for years - why is that OK in your book? Being neurodiverse is not an excuse for being a twat.

You haven't got a conflict between your daughters. You've got an abusive 18 year old and her victim. I'm telling you now that unless you stop your 18-year-old's behaviour and nip it in the bud, your youngest daughter will (rightfully) walk out of your life and not look back and you will be stuck with an abusive nightmare for the rest of your days. Your eldest's behaviour is absolutely unacceptable - so stop treating her like she's behaving properly. Cut out every single treat and focus on the daughter who knows how to behave appropriately.

I would love to hear about a case of an adult being sent to prison for ignoring a ND person who is behaving in an abusive manner. Absolutely ridiculous. Time to stop making excuses for bad behaviour.

I really feel for your second daughter. I have friends in a similar situation and the neurodiverse child has always been the focus of their attention and the other one is often ignored and spends her life stepping on eggshells. Your 18 year old is an adult and needs to learn to behave like one. There are probably some charities out there who can help you. You cannot let your child continue ruining everyone’s life.

Retrained!?!

She's not a dog. How insulting!

Very disablist!