What have been working for me its time and learning about how pwBPD go through life, how relationships evolve.
Accept the fact that you can't help them unless they take the first step and realize they indeed have a problem; i spoke with a BPD person in recovery and she told me that the worst part is accepting all the damage she had done and stop blaming everyone for it, they need to accept that and it seems they know deep down but the disorder won't let them take responsibility so thats why its so hard.
My advise stick to NC unless you are forced to speak with her, don't attempt to start a friendship right now if you still have feelings for her and accept the fact that 2 weeks without you its like 6 months without her for you, so trust me they will move on as soon as they find someone.
Its ok to feel hurt, i was devastated the day i found out she was with another guy and also about the things i found out but this forum and the experiences you can read will help you a lot to overcome the feelings.
Another thing, don't expect you are the exception to the rule, mine made that very clear.
I know I will see her at some point next month sadly, I'd feel it was much easier if I could just cut her out of my life completely but she is going to start living with mutual friends.