Hi bodichitta,
Sadly, what you describe is something we hear a lot around here. Here is some information about relationship recycling that can perhaps give you some insights;
https://bpdfamily.com/message_board/index.php?topic=95860.0 Hopefully others will join us here and share their ideas as well.
I know how painful it can be when someone "could go from being so in love to not wanting to see you."
I had a boyfriend once who declared "he would never, ever break up with me" and then did so very suddenly and without explanation less than a week later. It made me feel horrible.
Is this your first break up with her?