I don't know enough about BPD to weigh in to that possibility, but I do agree that something doesn't sound "right" about her reaction...even if she didn't want to continue a relationship, she should have at least been happy to see you again after such a time. Her displayed apathy is, to me, a red flag, not to even speak of her following actions.

I am so sorry you went through this...I am (unfortunately) very well aware of how much this hurts. I myself got out of an utterly toxic relationship a year ago this June. As much as I loathe to admit it, I still think about her often, and every now and then I still get fleeting pangs of feelings towards her...despite the fact that our entire relationship was a lie and the fact she utterly betrayed me. It does get better though...despite the fact I do still occasionally think about it, it's gotten infinitely better than from when it was fresh. You have to take some solace in the fact that ultimately, as much as this hurts, the ending to this relationship was likely for the best. She didn't have the consideration to treat you as you deserved, nor did she (I think) truly consider your feelings. God knows it hurts, but it gets better. Slowly, admittedly painfully slowly, but it does get better. And in the end, I believe you'll come out stronger for it.

Know you're not alone in this, and that you're in my thoughts and prayers.

Hugs,
Harley