Hey

Wow, you're right at the start of such a confusing journey... . I too remember being confused (still am), hurt, angry, sad... . a whole host of emotions. I couldn't understand how somebody who loved me THAT MUCH and said I was her reason for being alive, could leave me and straight away meet somebody else... .
I wish I could give you answers but I can't. The answers relating to a BPD can be so many, but also they just make me sad. Like the idea that you were just an object to that person. It just doesn't sit right with me, it really doesn't. Call me deluded but she loved me. She really did. At that point in time, I was her moon and her stars.
I read elsewhere (not about a BPD relationship though) that rebound relationships occur because the person has so many leftover feelings for YOU but doesn't know what to do with them, so projects them on to the next object. Who knows.
The soulmate thing is a killer... . it really is :'(
I wouldn't be surprised if she reaches out to you - not at all. How was she with other exes? The best predictor of the future is the past... .
She isn't "in love" - she loves what the new guy can do for her. It's self-serving... .
Where are you based? Maybe somebody can suggest free or low cost therapy. I've heard that a BPD relationship ending can be like PTSD and I think that is so true... .
Your story is so familiar... . read lots here, it really does help.
Wishing you the best x