How would you handle this?

Personally I think she should not have had all this contact with her exbf even if she still had some feelings for him. You are not doing anything wrong (she is imo) but it's tough to know waht to do with someone who still has feelings for their exes. Personally I'd be very close to breaking up right there. If I'm not the one and only guy in her mind (not counting just-friends) then it's over for me. And I'd expect my gf to expect the same loyalty from me.

As soon as I would have found out about the sex part I'd have left her I hold woman to same standards they hold me to, if i can keep it in my pants for one woman they can do the same

GAH I hate that situation, y cant ppl just be upfront about ur feelings i think ofcourse u sood let her see him but maybe have u go along to meet him and affirm to him that shes with u now (i think all that evidence shows she cant be trusted alone with him...no offense to her just emotions r a crazy thing) maybe get to be friends with him too, that wood be the best outcome but ur in a really tough situation, i hope u the best of luck

<font color="red"><strong>Phuck 'em. Just move on. You don't need someone who is "confused" about their feelings for you or another. It's never a good idea to see your ex. They are an EX for good reason ne? Personally nothing good came from seeing my ex. I cut ties severely and move on.</strong></font>

Not going to lie right now im questioning the relationship entirely she cries over him leaving and then asks to see him then says she might have.sex with him and I feel like you are trying to hard to be nice about the situation. Ultimately its your choice but at the very least you should go with her

I think you're handling it well. Humans are humans, and human relationships with one another are complex things. The key really is to have a strong level of communication. That's how you can really trust each other. It seems like you guys are pretty good since when you confronted her about the sex bit, she didn't deny it. I'd probably just let her know exactly how you feel and that you trust her. Maybe a good talk will help you feel a bit better about it. In the end, you gotta trust the other person. Otherwise there's no point in being in a relationship ya know? But seriously, kudos for how you're handling this