Does this feel good to girls..?

im 18 and my girlfriend is 17. anyways, we were making out on her couch and things got intense so i moved my hand to her "lower area" and started rubbing her back and forth through her shorts. this went on for about 30 minutes and we were just staring at each other in the eyes during this process and i could hear her breathing heavily as if she was shivering as she was inhaling and exhaling, but it wasn't cold at all. was this because she enjoyed it? did this make her uncomfortable? this was our first time experiencing something like this. and also, i played with her for a while afterwards and her were really hard and it wasn't cold. what does this mean?