So to make a long story short my ex and I dated for about a year and eight months. Things got stagnant, boring, and change. I was doing a lot of nothing with my life and didn't really care about much. I got completely codependent on her for all of my emotional needs and pretty much most of my life. She got tired of the constant fighting, things staying the same, and fell out of love. So we did the typical no talk for a while which got interrupted quite a bit due to immature fights stemming from social media and not being able to not talk. I ended up jumping into a relationship on impulse, lo and behold she came running back. At first I treated what she had to say with skepticism because I just thought yeah this is just a typical ex-comes-running-back situation until I realized what she was saying actually came from the heart because it wasn't typical of what I've heard in the past with those situations.
That's just some back up story to this, now for my actual concern. So we started hanging out again and then for a good three weeks she was scared she had mono but the doctors couldn't figure out what was wrong. She came to find out that she had mono antibodies but the doctors said it was probably from a past infection because her blood work at the peak of her being sick weren't suggestive of mono. So that led me to raise the question "Who did you get mono from?" She said the only person she's kissed was a friend named Alex after we broke up (I've always had one of those keep an eye on feelings about the kid). So I questioned her some more about and she said she didn't feel comfortable talking about but would tell me anyway what happened. "We didn't have sex. He took off my bra, grabbed my ass, and rubbed me through my pants. He kept trying to have sex with me but I refused because it didn't feel right because I was an emotional cluster**** and was right out of the relationship and still had some feelings for you. He kept trying to say what does it matter you're not in a relationship and I repeatedly explained to him." I kept asking questions about the situation. She said that she came on to him, so naturally I asked why. She kinda got this look on her face and said I don't know. I kinda laughed and said "yeah.... right, you know". She said she knew and "it was just a thing". So I left it at that for the time being, but what's messing with me is "just a thing" is suggestive of something going on before, maybe not physical but emotional or talking.
What are your thoughts? I really don't know where to move on from here. I know I'm gonna talk to her about it some more since talking about issues is the best thing to do when you have a problem. The kid has been respectful in the past when we were in a relationship. He's even told people to back up when they tried to make a move on her when I wasn't there. I always knew the kid liked her (She's known the kid since middle or elementary school). I know she wouldn't cheat on me but part of me can't help to think, is this something that could happen again but escalate? This situation has pretty much thrown out the whole him being a good friend and pretty much turned him into a snake in the bushes like everyone was telling me he was. I'm just confused, and part of whats making me question if I even want to move forward with her is because I know she's going to be around him again when alcohol is present (She's a very in control of her actions type of drunk, she's not the type to cheat because she's drunk). Part of me is says, this is no big deal because I had sex with two different people during the split up, but those were people I had no feelings for and pretty much quit talking to right after it happened. This however is someone she said was a good friend and she almost had sex with the kid.
Thoughts? Am I over thinking? Advice?