Did my girlfriend orgasm?

Well, we were at my house on the floor making out and I was rubbing her vagina (on top of clothes) and she started kissing me back really hard all of a sudden, and then sortof went limp and rolled her head to the side. I wasn't really sure if she'd orgasmed or not, we were both breathing really hard, and I've never had a girlfriend before, so I'm not sure how to tell...