hi BPDbestfriend92 and
i'm so sorry for your situation and i hope you'll get good support here. we have an active community of members and a wealth of resources for people who are dealing with BPD from every angle. on the right hand side of this board there are readings which have been prepared by experienced students of BPD; please have a look over there sometime.
it's not uncommon to be caught between the decent urge to help friends and the need to take care of ourselves. i have been in the situation where i had to take care of myself, to take care of another. you are in a high-stress situation. what support do you have? do you have family or a counselor with whom you can talk things out? how do you and her other friends share responsibilities? please keep posting BPDbestfriend92!