Daughter's friend's mum love bombing my daughter and it feels so uncomfortable

I noticed that with the only child parents might behave like this to make sure that they are involved in child’s life, another reason might be additional needs of the child (but it doesn’t seem to be in this case) or it could be that the other family is problematic in some way (e.g alcohol or drugs which is obviously not the case with you) .
I wouldn’t like my DD being a part of other family - she is part of mine. Something is not right in here. This girl’s attitude towards you means that she is hiding something:her feelings about you for some reason or general distrust towards other adults again for some reason.
By the way could it be that this girl is gay and interested in your DD ? I know they know each other for 5 years but still.
You have to keep digging and invite them more to yours. Your advantage is that you know this mum so plan ahead all responses and don’t be shy to be not rude but rather unpredictably and politely stubborn . Answer no and that’s it.
I think your DD needs a new hobby etc towards uni. You don’t want them to go to the same place do you?

I hope I'm not being weird here but it sounds creepy and groomy. I wouldn't like it.

Do you feel like she’s one of those “My daughter is my best friend” mums? I always find them overly-invested and frequently immature/insecure. You can have a close, loving relationship without trying to be their friend. They need a parent.

I imagine she doesn’t really have an ‘end game’ as such. She is just following and doing what feels good to her and not giving much thought about what feels good for anyone else. Following her instincts and noticing opportunities.

You do need to set boundaries and you need to teach your daughters to set boundaries by example.

How about starting with practising the classic, catch-all phrase “this doesn’t suit me”?

And this is an even bigger problem. Much as I want my Dc to get on well with many kids and their families, I would push back firmly if another woman talked about one of my DC as being in her family. It’s great to say that other people’s DC are a pleasure to look after, welcome any time etc but not to say they’re a third son etc.

This mum sounds like an absolute nut job. Gently take the piss out of her to your daughter, easy does it! Find out your daughter's opinion of this mum, your daughter's not stupid, if the mum's a weirdo she'll know. This woman is desperately insecure and wants to be the centre of everything. No one is going to take your daughter away from you. Don't let this women create a space between you and your daughter by making you feel that she's closer to your own child. As that's what she wants. Be open with your daughter, tell her this mum's well weird with you. Don't doubt yourself. X

Ok, so this is an issue. I’d make it clear that the sleepover will be at yours because you’d like to have them over (unless her daughter has a medical issue?)

That’s so bloody rude. To call your daughter her daughter. I can understand that sort of thing being comforting for a child who has lost or been abandoned by their mother, or if the mother is in prison or terminally ill and worried about what will happen to them when she’s not around, but when you are living, breathing, present, willing and able as a mother, it is completely off. Totally overstepping the mark. And I think she might even be enjoying the distress it causes you- some kind of weird power trip.

This happened with DS1. When he came out as gay, the mother of a friend of his made him a massive rainbow cake and then baked brownies for him to take to LGBT meetings. I was totally fine with him being gay but felt spectacularly inadequate on the baking front! Then his mate's girlfriend dumped him just before his school leaving prom. I overheard the mother excitedly telling a friend that he was inviting my son as his date instead (which he did, even though he was straight, as they were good mates.) The way she said his name gave me the creeps, as if she had an infatuation with him and couldn't stop saying his name. I asked Ds about it and he said, she does keep asking if she can adopt me and I have told her I have a mum I'm happy with. Obviously she was being light-hearted but still, it was all a bit OTT.

It did unsettle me, as I'd always felt I had a very strong relationship with DS but DS2 had a lot of complex needs and I was conscious that DS1 was left to get on with things a fair bit. I worried that I'd neglected him. But he said not.

Have you considered that the other mum has misgivings about you, which is why she wants the girls to stay at her place and not at yours?

sorry, really not normal for YOUR best friend’s daughter to be calling you when she’s pissed off with her and downright odd if it’s your presumably male partner she’s calling.

I wouldn't like it either, but your dd is 17 so it's a bit late to try and change the dynamics.

I agree with you it's the pushing boundaries/lack of respect that the issue. Plus she sounds hard work!

It may be she's very over protective of her child and quite needy herself.

Unless you have significant concerns I'd be firm with boundaries and look forward to when this is no longer your problem

It doesn’t sound as warm and friendly at all from OP’s examples especially the one about joint birthday party

Wow, it’s very very weird. It’s not something maybe off the whole concept of relationship is very off.
For some reason she wants to keep your daughter sort of “with them “ . The most obvious reason is that she is controlling towards her daughter and afraid about her daughter to go away at the first opportunity. To keep daughter close she is using your daughter.
Is this girl an only child by the way?

This crossed my mind. Does friends mum have a partner op??
I think her behaviour is inappropriate.

Some people are just like that - warm and friendly. I've always been very close to my friend's mum (since the age of 5). She was like a second mum to me and always hugged me and treated me like one of the family. Now I'm 49 and she's terminally ill in her 80s. I still visit her her and will be bereft when she dies.
I don't see how you can reasonably object to a close relationship between two people.

she'll always have the advantage in that regard

I know you might just be using this as a turn of phrase @Winterslopes, but this language makes it seem as though your insecurities are really triggered and you are perceiving this all from the perspective of this woman being a threat, a competitor in your mother-daughter relationship, and that you need to defend yourself and fight for your life.

Take on board what @itsgoingtobealright said about you being the mum. The one and only. You can’t be replaced.

All the triggered emotions you are experiencing, because this is your deepest wound and insecurity, are stopping you from taking comfort in the objective truth.

You are the mum and your children will irrationally adore you. It is both an un-earned blessing and a huge responsibility.

You are right to be cautious.
It sounds like she's seeking narcissistic supply!

Sounds like a competitiveness on her part. She likes to railroad you. Pick a few boundaries with her and maintain them e.g. the sleepovers...start slowly. Be persistent even if she becomes shirty with you. You do not have to explain to your daughter as she will learn about boundaries by watching you. She will also learn how to say No.

Entirely reasonable of you to feel this way about this