Should I trust her after what happened?

I think you should trust her. If something had happened, she wouldn't have told you anything. If anything happened would he be sleeping on the floor and would she be on the bed fully clothed? Probably not. I think the guy that let her stay over was just a nice guy that felt bad for her and wanted to make sure she was safe. She cares enough about you to want to be honest with you and tell you about it, even though nothing happened.