hmmmm - sounds complicated. are there things that work well with her where you can actively keep that relationship and do those things, and then (with her knowing) you can work with someone else on the relational stuff? Like a back up T for her and you? I read that in a DID book (and they said BPD is similiar in a lot of ways) and it looked like a viable option (to me).
Kiya
Hope this works out!