pwBPD are survivors, so even when it seems like they have no one left, they will likely bounce back and find a new supply.
Three months ago, my former friend BPD was in the psych ward. Other than her parents, the only people who visited her were me and her boyfriend. Fast forward a week, and she ends our friendship. Fast forward two months, and she breaks up with her boyfriend. Fast forward a few weeks after that, and she is desperately trying to find somewhere to live here, instead of going to live with her parents.
A few weeks ago, she even asked me if she could live with me. But now, she's found an apartment, is getting a promotion at work soon, and has apparently made all kinds of new friends, since she told me last night that all sorts of people she knows now think I'm crazy. So basically, a bunch of people who work with her at a convenience store/gas station think I'm crazy. And I'm apparently supposed to care about this,

.
I know how hard it can be, but at the end of the day, you're the mentally healthy one, and you have a chance to be happy. My former friend BPD was formally diagnosed and said she was going to get help, but she changed her mind a few weeks later.