I feel like I’m loosing my best friend, what do I do?

My best friend and I have been friends for just over 2 years things were fine up until about a year ago when she started to change and want more friends, which she says is because she wants different opinions which I get but I don’t feel like that’s why she’s doing it as she won’t even listen to my opinion anymore, but anyway she starting becoming friends with old people who were mean to me in the past and it was having a huge impact on my mental health and then she re connected with an old friend from one of her teen mum groups who she’d fell out with in the past because she’d said bad things about her, this had a huge impact on my mental health as she’d told me just months prior she’d never need any other friends etc and now everything was changing which I couldn’t handle this went on for a few months and then things felt like they were going back to normal and then we had a big falling out and from then my mental health went down hill and i was diagnosed with borderline personality disorder which took a huge toll on me mentally, physically and emotionally but I tried to keep it together and it was easy because my friend was always there and then she became my favourite person and I relied on her heavily and I know now how much of a toll that took on her and the attachment was out of my control and I feel like she always blames me for it when I wish I could change it, recently I had a breakdown and ended up trying to commit suicide and her boyfriend (now ex) and this other friend from the mum group got involved and things ended really badly and they were awful to me and called me awful things and I feel like in the end my friend sided with them and her having them in her life was and is still having a huge impact on my mental health and I truly don’t think I can get over this period with the friend and the constant anxiety and worry that the boyfriend is gonna come back because it brings all the intense feelings of that really bad time back everytime I know she’s talking to them or she talks about them and it brings me back to the night and I don’t like it and can’t handle it anymore I just need it to stop, lately I’ve noticed her pulling away from me being more secretive hiding things etc and I don’t feel like our friendship can work if I’m being fully 100% honest with her and she’s hiding 99% of things she won’t even tell me how she’s feeling if I ask how she is

I don’t know what to do because I don’t want to loose her she’s the most important person in the world to me and I don’t think I can cope without her

Ps I am in counselling and do receive help from a professional