So I hope this is the right place to post this, if not I apologize in advance. 

So I have a friend who has BPD and I don’t really know how to support them. The biggest problem is that before I knew they had BPD I confessed that I had feelings for her. We had been friends for a while and during this conversation she basically said she wasn’t ready for a relationship because of her BPD. She is actively working on it and I try to support her as best as I can but other then being stable and non reactive what should I do? I told her I understood and that I respect her decision and am happy staying friends. The issue is anytime another girl shows interest in me or it looks like I may start dating someone else she tends to become extremely upset. For example I had a drink with a close female friend and we posted about it on social media and it looked like we were a couple. This caused her to oscillate between extreme anger like hitting things and destroying objects to extreme sadness and crying. This lasted until I volunteered the info that the girl she saw me with was only a friend and had a partner already. This is made worse because my friend has few friends  that will do things with her. Really she only has two other close friends and one is actively distancing herself currently. So really only one other friend. I want to help her and be a supportive friend because I care for her, but also I don’t know what to do if I want to date someone. 

To be clear I don’t have any issue with her having BPD and I am not pushing for a relationship.

TLDR: my friend has BPD I found out after I asked her out, we stayed friends and I want to try and support her but she is extremely possessive and I don’t know what to do.