[Age of Ignorance]

Wow, dude. I feel for you.

My understanding of the situation is that she concocted this story about how she "had" to go over there, as Robin has said, and that she kissed him "but didn't like it", and that she refused to have sex with him "because of you." Just... wow. If she respected your feelings, she wouldn't have gone there, she wouldn't have kissed him, and she wouldn't have gotten into a situation where she had to "refuse to have sex" with him. Plus, it appears she lied to him as well, about you slapping her and forcing her to kiss you. So, she's lying, in part, to both of you. She's playing you both.

I suggest you take a step back from the situation, and assess it from an outward point of view. Try to push all the emotional turmoil to the side for one moment, and think of it as a jigsaw puzzle. If a piece doesn't seem to fit right, it probably doesn't, and you can assume it means something else.

I'd also suggest you talk to her about this. If she confessed that she kissed her ex and almost had sex with him, then she's part of the way there. If your "outward point of view" assessment reveals things that "just don't fit", then bring them up. Tell her that you don't think the reason fits or that it doesn't make sense to you.

Just remember, poke holes in the story until you feel comfortable and armed enough to confront her about it. I'm sure you can make your own assessment as to whether or not to stay with her. If it were me, though, I'd get out of there fast.