Hi everyone, really sorry if this is the wrong subreddit to post in - I'm at my wits' end trying to find advice online to help me support a friend of mine who has BPD. 

We have been friends for several years and there have inevitably been ups and downs, but in general everything has been ok. 

Recently, a mutual friend of ours who I am close to (I will call them A to make it easier) chose to step back from their friendship with my friend with BPD (I'll call them B). This was because our friend has difficulty controlling their anger with others and will often become very aggressive at short notice. B has told us before that this is because their BPD makes it hard to regulate how they're feeling when distressed. They are doing an amazing job with seeking therapy, getting input from mental health professionals etc, but I know it is a long road and things are still inevitably going to be difficult. 

The reason why I explained about A breaking off their friendship with friend B is because B has now, in a short space of time, decided that the reason for this happening is me - they are convinced that I somehow forced A to end their friendship and am now going around talking to other mutual friends and convincing them to also cut B off. This is based off of literally nothing - A and I are close friends but we have never had a conversation where I told her to do anything of the sort. 

B has now suddenly blocked me on social media and sent me messages saying they don't want to be friends anymore. They are also starting to make posts alluding to me being a bad person etc. More than anything I'm worried about B - there is genuinely no evidence that could suggest I've been going behind their back or talking badly of them. I haven't spoken to anyone about them or said anything of the sort. I know they have said before they find it difficult to not feel abandoned / to trust others because of their BPD. I felt like maybe that's relevant here. 

My question is, is there a way I can support them with this, even if they are suddenly saying they don't want anything to do with me? Is it better for me to take a step back? I'm really worried for them right now, and if I am truly honest I kind of resent being treated like a villain when I haven't actually done anything wrong. 

Thank you so much for reading, really sorry if this is incorrectly formatted or in the wrong place!