MPD, now termed DID, sounds tough, but at least she was honest.
We have a discussion here:
COMPARISON: Dissociative Identity DisorderIf solely BPD, I would say that she might be distancing herself due to the core shame of a pwBPD ("I don't matter, I'm unlovable"), yet DID is another thing entirely, even if pwBPD manifest dissociative behaviors.
Do you perceive any trigger either on your part or something that happened? It sounds like you communicated well (see the tools in Lesson 3 at the top of the board for more).
I think helping her, no matter how well intentioned, might trigger more shame or fleeing behaviour. Focusing on what you can do on your side of the fence might be better. What did you think?