If you trust her, dont betray her trust by being suspicious of her, if you don't trust her you shouldn't be with her.

That's my take for what its worth. I've had a girlfriend cheat on me before, I broke the guys nose, then I let her know what I thought of her, and then moved on with my life.

I never snooped on her or any shit like that, you eithier trust someone or you dont.