What's this girls issue?

There's this girl a year younger than me in 9th grade. Everyone kind of wrote her off when she was in 7th grade for cutting herself so I'd never heard of her until someone she was kind of friends with told me she liked me. I saw her and she was really pretty so I went to her at lunch and sat down, she just collected her things and left. I tried talking to he again but she just walks away. We had this Banquet thing that was mandatory to attend. I was looking for her and found her by herself in the gym listening to her ipod behind the bleachers. I said hi and told her to come out and dance and stuff and she just screams "stop talking to me like i'm a ******* baby!" and runs out I dont get what her problem is I've barely spoken to her. Anyone have any idea what could have got her so mad or how to make it better?