Please don't feel guilty, brzghoff. Any relationship with BPD person is a toxic one. You need to take care of yourself right now and with BPD comes a lot of drama. They need to be the center of attention. If they're not, they will do something to make them the center of attention.
I have had plenty of exposure to at least half a dozen people with this disorder. Mainly while I was hospitalized for nearly 2 years and my own daughter most likely has BPD. I treat them with respect but I won't let them suck me into their illness. Once they realize they can't manipulate me, they don't want to bother with me anymore but I think they have respect for me in the end.
I have been in group therapy called DBT (Dialectical behavior therapy) which is supposed to treat BPD. Maybe it was because we were required to get this treatment and didn't seek help on our own, but in my experiance, It didn't help much. It just got us off the locked unit for an hour and a half a day.
PS. I don't have BPD. I had severe depression. (just fyi)