Much of what you say in your post is very familiar. I think low contact might work for a while but my guess is when she gets very down she will try and recycle or triangulate you with her new love, it might be impossible.
good luck
Im not too worried about a recycle. From her past relationships, she's never attempted it. But then again, who knows. Before me she's always had someone lined up. This time however, she's struggling to make a connection with anyone. I mean, there will always be a part of me that still wants to attempt to have a relationship again with the person I knew. Im not one to hold a grudge on anyone; whats in the past is the past to me. I do have boundaries as to what I will and wont tolerate though, and a romantic relationship is out of the question with the person she's become.
Triangulation
(read definition), perhaps. But that takes a third person. She's more the type to stalk you on social media like facebook or twitter to find out what's up. Which, often times just makes her more upset because then she sees how much fun everyone is having with out her.
I know its somewhat common traits of a pwBPD, but may I ask what makes you think she may attempt to try something though?