My long-distance girlfriend gave me her Facebook login because I had a couple of doubts and came clean to her. She let me log in to it, but told me to stay off her friends chat. I did at first, but then curiosity got me. I went back about 4 weeks and I found that the guy she stopped talking to had cuddled with her every time she hung out with him at his house (About 4-6 times). A couple of the times, they kissed or made out as well, I asked her about him, and she said that they don’t talk or hang out and didn’t ever do anything remotely sexual. Do I call her out on it? Do I stay quiet and believe her?
LemonVibe 
Admit what you saw and tell her how you feel about it.
I am going to be honest though. It skeeves me out that you felt the need to spy in her Facebook account. It makes me just as uncomfortable when women do that to men. She was wrong to make out with the guy (I don’t see a cuddle as a offense but kisses or petting crosses the line in my personal book) and you were wrong to break her trust by going in her messages.