Should I be mad at my girlfriend?

[Zach]

Hello

I've been with my girlfriend for 3 months, and we're both 17. I went to change something on my girlfriends facebook and was asked to check her message from her friend since she wasn't on her computer cause it broke. Anyways, in her chat log there was a chat from a guy. We started going out August 25, and the date of the conversation was September 6th so we were going out at the time. He rated her, and she said "thannks". When I say rate I mean like he made a status going "like my status and I'll rate you from 1-10" on looks. It kind of bothered me this discovery because we were going out. I know she also talked to this boy in the past and never got with him, but she did have an attraction towards him. I feel as if she liked that status in hopes to try and talk to him, because they have talked previously. I do trust her but it feels weird.. like she went behind my back and did something. I brought this up to her and she said she doesn't remember doing that and that she's very sorry and she cried because she knows that she'd get mad if I did that to her. She does a lot to show that she loves me and I don't know should I still trust her? She didn't cheat but it feels iffy..maybe I'm just overthinking?

What should I do?

Thanks for reading!