From my experience cluster Bs can form a lovefest for a small length of time lasting at the most a few weeks, and then expect that love to turn into intense hate.
I remember there were two residents (I'm not being sarcastic) that both had cluster B disorders and they had the lovefest for weeks. One of these had falsely accused other people of the program of raping her. The other wrote a letter to the faculty in total support of this other resident because she knew the first resident was put under a microscope due to her false claims.
A few weeks later, they were bitter enemies, and now the resident that wrote the letter was claiming I had a sexual relationship with the other resident. (Wasn't true and the only evidence she had to back this up was that I was telling other people to not get involved with this and let the faculty deal with this).
The 2nd resident several months later is now back into love mode with me and is telling me how she hates a bunch of other residents, then is telling an attending that I got a personality disorder.
The first resident was kicked out, the 2nd ended up going to a namebrand fellowship.
When dealing with a borderline, you have to set your boundaries and stick to them. IF they're pissed with you, too bad. Don't put so much weight that they're mad at you. Put more focus on you sticking to the boundaries and doing something that is therapeutic without giving in to the lovefest, when they do happen.