Hi. I'm a girl and I too and have 2 guy friends that I hang out a lot with. And I think it's ok for girls to have male friends. But, your gf has cheated on you, one thing I never did with any of my boyfriends. I think you do love her a lot and are afraid of loosing her. And that way you may not be very impartial when it comes to seeing what it's really going on. I think that women who cheat once(or men) will do it again. But that is just my opinion. Maybe talking to her really honest and trying to analyze this situation very rationally(I know that might be hard) could help you make a decision.

To answer your question, no, I don't think you are being too insecure. You have reasons to feel that way.
If you just can't bring yourself to trust her you can't just force it to happen.