My stepdad gave me some good advice for life the other night, I'll share it with you.

"Just remember that if you have a pretty girl as a girlfriend or wife or whatever, everyone else is going to want her too, so its best to not let it bother you."

I went through that with my ex-girlfriend, every fucking guy looked at her or flirted with her and I'm a jealous guy who let it get to me. If she really is fine, you best get use to it and not let it bother you. There's nothing wrong with a guy looking at a girl or talking to her so you can't give him shit for that really..but, I'm not saying you can't kick his ass if he starts being mean or derogatory towards her.