I think everyone pretty much has the bases covered.

I want to reiterate that jealously is poison. Especially if you let that fear take over your mind. The best way to combat is be yourself. Just have some fun with your gf. After all, that's why you are together. Don't forget the good times, and don't let yourself get poisoned with "possibilities."

If she's going to cheat on you, she'll do it regardless whether the dude likes her or not. I been that dude, and well, let's say it has a happy ending for me. She wouldn't be the one for you anyway. But don't throw poison in the well to perpetuate it.