To politely ask this mum to back off a little?

This* neurodiversity is 70% as inheritible as height. Being "very intense & anxious " is probably because she has asd too. I would just be polite and say I am busy /can't talk right now .

This, plus you are not her therapist dont get involved in the drama tell her and move on in your life

Clearly giving hints isn't working. If she is indeed autistic, just tell her straight, she'll appreciate the clarity.

"Claire, I'm sorry but I don't have the capacity or time for phone calls/texts/a new friendship. I have a lot going on in my own life. The odd playdate for DD & YourDD once a month is all I can manage, nothing more. As I said, here are some helplines. Hopefully they can give you the help that I can't."

Don’t make the mistake of spending ages until you’re exhausted counselling someone who doesn’t actually want advice or signposting but just wants someone to endlessly offload on.

What did she say when she saw you?

Do you think she ‘got it’?

What stands out for me is that despite you sending texts saying you’re busy etc, there was still a
phone call, so she got what she wanted really.

I think you’ll have to be firmer with her unfortunately.

I can (shock, horror), be quite blunt. With people wanting friendship, I tend to be quite clear about my limitations/boundaries as a friend. I am not a 'besties forever/contact every day' friend, I just don't have it in me. So if that's what they're wanting, they're going to be disappointed, so perhaps we're not a good friend fit, and they should look elsewhere.

You have so much going on in your life. You simply don't have the bandwidth she wants or needs, and that is okay. That doesn't make you a bad person. (In fact, you sound an incredibly lovely person.)

I think you need to stop completely with the calls. Either make up a long lasting excuse eg you are at work and very busy or tell her outright that you dont feel able to advise her and you are very uncomfortable with her relying on you for support and you want her to get support elsewhere.

Just be upfront, say you feel awkward about bumping in to her when you said you were out of town but the truth is that you're finding the amount of messaging/ talking overwhelming and wanted to create some space.

You don't need to elaborate, say you have a lot on your plate and you don't have the time/ head space to cultivate a new friendship right now. If you want to keep the door open for future meet ups you can add that you hope the girls can have the occasional play date in the future/ when you have time to arrange you'll be in touch.

Do exactly what @5128gap says. No need to lie about being somewhere else — you just say ‘That’s jot going to work for me.’. Don’t pick up the phone. You’re not her MH support worker. She’s the parent of your child’s friend, and you can see exactly why she doesn’t have any friends, and is dumping her distress on someone she barely knows because it hasn’t occurred to her that it’s completely inappropriate. You’re going to have to take control more.

What SEN groups are local to you perhaps you could suggest meeting at one together in the hope of introducing her to the local community?

Agree with the message back when you can not straight away

Never make your excuses not to meet or talk too detailed.
If you’d just stopped at “sorry can’t meet today I’m super busy” then when you saw her at the bus stop you could have just said “yes I’m busy & on my way out - can’t stop to chat now”
You being ‘busy’ can mean that you’ve decided to hoover the floors or something, that’s how you’ve decided to arrange your day - you do not owe her any of your time or any explanation/justification on what you do with your precious time.
You probably should say to her that calling and messaging you multiple times a day is too much as it’s causing you stress.

Don't feel bad.
You have to care of you and it appears she's not the type of person to take a hint. So you have to do & had to do what you had & have to do.

Hopefully, she gets the hint now.

If she is in therapy for her mental health then you should be honest. She will understand if you say that due to your own mental health situation you are struggling with self care and not able to take on the position of being her listener right now.

I was just about to mention people pleasing. I'm prone to doing it and I've found myself caught in the orbit of needy people like this too over the years, where I would start off thinking I was being nice and then a few weeks later think WTF and realise I was being completely and utterly used and that I was angry and miserable. I think the problem we have is that we allow ourselves to be roped in too quickly - we're handing over a phone number before we've had a chance to know if we really want them to have it, whereas people who aren't people pleasers don't let themselves be moved that fast.

The big problem isn't her, it's how you handle the guilt you feel when you say no, and the fear of making someone else disappointed. Yes, she's clearly lonely and having a difficult time, but this is not your problem to solve. You are not free therapy or a dumpster she can use to offload her emotions into. It's not your job to save her from difficult feelings. Let her feel them. It's not mean or cruel. It's adult and normal.

It's alright to say no. I know it goes against everything we've been told (which is what made us into people pleasers in the first place) but it really is OK to disappoint other people and put your own needs first. And other people really will survive if left to sit with their own negative feelings.

There's a really good book called codependent no more by Melody Beattie which I recommend, it put a whole new slant on this behaviour for me.

Definitely be less 'available', so no face-times or constant stream of messages. Keep reiterating that you are so busy, life is crazy lately etc etc, hopefully she will start to get the message your not available emotionally to her in this way, but I would't ask her to 'back off' or ignore her completely. The friendship is beneficial for your daughter too, so I'd suck it up a little bit with that in mind.

I wouldn't ask her to back off in so many words, as you don't want her to take it the wrong way and create bad blood, particularly if the kids end up going to the same school. I would really cut down on contact with her though. Don't reply to every message and ignore her when you don't want to answer her calls. If she asks why, just tell her you're busy. She will get the message and realise sooner or later that it's one sided. She can only take up all your time and attention if you're willing to give it.

I think this is a show not tell situation. There usually isn't a nice way to tell someone to back off, because often the people who take up too much of our time are in need of some sort, vulnerable and will be easily hurt and rejected. So I think the best course of action is to establish your boundaries and then wean her off until she's behind your line. So gradually take longer to respond to her messages and be briefer with your replies (warm and friendly, but brief with no questions to encourage conversation). Don't answer voice calls, ever. Just message her back telling her you were busy and are available (set time). I would tell her the video calls with the girls aren't working out, and suggest they're better on playdates (offered at a frequency you're comfortable with). Basically you need to take control here, and gradually pull this relationship back so it aligns with your offer rather than allowing her to dictate it.

I wouldn’t ask her to back off but I would not answer the phone to her. I’d reply briefly to each message by text saying things like Gosh sorry that sounds tough. I’m up to my eyes this week and can’t talk but hope it goes well. And say you don’t think the FaceTime is working, let the girls meet in real life instead.

‘Sorry I was so busy with the kids yesterday I haven’t even had time to sit down and go through my messages yet!’.

just be less available. Just because the phone rings, doesn’t mean you have to answer it.

She has a need she wants meet. You see it, feel it, understand it and could meet it… but only at the expense of your own wellbeing. People pleasing is a survival strategy. Usually developed as a child in a maladaptive environment where people pleasing helped you feel safe and get your needs met. But over decades it literally burns your body out.
I find imaging I’m physically dragging myself into my own body and put an invisible shield around works for me. You’re you and it’s your job to meet your needs. If she can’t meet her own needs then she needs to get professional help to learn to do that - not try and make you an appendage/tool in her life.
I sense from your posts (but could be projecting) that ignore her “hooks” asking for help makes you feel unsafe somehow. That’s why it’s hard to know how you want to handle your interactions. Go for the friendship you want with her & don’t accept anything else. But also be aware she gets the right to say the type of friendship you want doesn’t work for her. That’s fine too. If you’ve been indulging her then she will have a reaction to that, I suspect. After the reaction, you can have a more balanced friendship or she might walk away. Both options are fine. You’ll be fine either way. If she’s childish and blanks you or otherwise behaves unkindly then label it. Ideally something humorous to you. We rated my MIL on her behaviour out of 10. (Ooh she put loads of thought into that comment give it a 10!) and it really took the sting out of it for my DH and me. She doesn’t bother much anymore becusse we’ve changed how we react.

If shes in the early stages of getting her daughter diagnosed she might be feeling overwhelmed hence her clinging to you
Not that you should have too but are there any local autism groups, charities parents forums, etc that you can direct her too ?

I'd just add to the good advice above, please don't just ignore her. She misread the friendship (for whatever reason) so to gently distance her would be kinder. "I don't always have time to deal with my phone, so apologies if it takes me a while to get back to you" messages should do the trick. Good luck x

All the best, OP. And well done on taking that first step.
The more you keep your boundaries, the easier it becomes.

Very hard for a people pleaser but it is a fantastic skill to have. Life suddenly feels less anxiety-inducing.