Your post brought up some memories of my break up over a year ago because I went through something extremely similar to you back then. Twisted female friend planting bullshit in her head, random encounter with some dude suddenly makes her get the tingles, etc.
Here's the thing, I could sit here and regale you with my own personal story and help you feel better, but I won't because it will not help you. You're in a fucked up mental position right now, you're trying to understand this woman who acted like she worshipped you could so suddenly become another person who was so willing to drop you without any regret. You need to sit in the anger phase, you need to read the sidebar, you need to read the men's right's posts here and the blue pill posts, and the other similar stories to yours because you need these thing to reset your brain. If you're doing it right, you'll begin to hate her and all other women because you'll begin to learn how fucking similar they are, you'll learn AWALT and it will hurt and it will piss you off...
Worst part? The bitch will come back at some point, she will. Trust me... she fucking will. Here's the thing though, you're going to ignore her and you're not going to feed her ego with your attention and second chances, because this is now all about you. She left, so fuck her, because you're going to stay mad and you're going to get angry and your going to let that anger wash over your mind in a form of cathartic healing and improvement. You're going to be a fucking better man. You don't need her and you don't need these wishy washy cunts. If you can fuck a few, no strings attached along the way, cool, wear a rubber and get yours and don't give a fuck about them. Otherwise, focus on yourself and focus on reforging those friendships you've let slide over the years and focus on making new ones.
It will get better, but only if you ignore the cunt, strike her from your mind, walk forward and never look back.