I am moving further from the belief in the fallacy of love which is really more a word to deem ones' over attachment and usually neediness toward another person. The ego then returns to hate, possessive, jealousy, and a bunch of nasty behavior once certain expectations are not met. I feel like you got swung and caught up in the moment. The feeling you have for her is likely real to you and from your perspective. A quality person would be forth right and up front ending a relationship rather then cheating blatantly on someone.
I ran into a girl I felt like I hit it off. She had been under the influence. Being the "good guy" that I am, I took her number, and planned to call her. Nothing happened dude. She probably banged some other dude that night. I ended up leaving with someone else which was a bad decision. All you can say is you did, you tried your best, and when you look back, no regrets.
I do not know this woman but, I would imagine she is the tragic female chameleon regardless of her circumstances or personal issues. Six years of a relationship and that man is a cuckold.
I don't want to live on this planet anymore.