Are my friends using me?

I had a sleepover with two girls....you would consider popular. I am not a geek or popular. I am that middle crowd. We went to see new moon, and we were all laughing and listening to music before and after and we even watched twilight. We fell asleep, and everyone was happy. This morning it was totally different. It was like they were mad or annoyed at me. The kept to themselves and kept asking when it was time to leave. Were they using me to just go see the movie? Was it because my stepmom mad them go home so early because she had a hair appointment? were they tired? or are the just preps that go to everyones sleepovers and parties just to go and keep their so called ranking?