1. I have to trust the girl I am with
2. I have to be willing to dump her immediately if she cheats on me. No wishy washy. I make it clear. You don't get to fuck that up. If you do, it is over.
3. I am going to have a problem with all of her male friends to some extent because even though I trust her, I won't trust that they don't have other intentions.
I will say this ... I have had friends with wives who were smoking hot but I never, ever thought of them sexually in any serious way. Even after one of them got divorced, I just couldn't look at that girl without thinking of her as the girl of my buddy and there was just zero desire for that person, even though she was good looking, generally a good person, responsible, hard working etc. etc. ... she was a friend and nothing more and nothing less, though without her being with my buddy anymore, she was just pretty much removed from my life. I find it super easy to draw that line in my mind, but seem to have a harder time with the wife of someone I don't know. But the point is .. I think you CAN make that distinction if you train yourself and you don't have to go gay to do it.
But bottom line … trust the girl you are with or she isn't worth being with and if she messes it up, be perfectly fine with letting the relationship go. No second chances on that one.
I would probably have a hard time with the guy friend person though, knowing what is most likely on his mind.