What's wrong with her?

Ok so today was the last day of school for me. But there is this really pretty popular girl who I always wanted to be friends with. ( we were in the same homeroom, had the same lunch period and even live in the same neighborhood!) She literally lived about 5 houses from me. But anyway today at lunch i decided to talk to her since I know we would be volunteering at the same kid camp in our town I know this because she was there signing up the same time I was. I went up to her and said Hi and began to talk but she just looked at me, gave me a nasty snarl and walked away! I felt sort of humiliated :(. This isn't the first time either, one time in homeroom I asked her if I could borrow a pencil and she just looked at me and looked away like she didn't even hear me! What's wrong with her? I am not ugly looking or have nasty teeth or anything, why does she act like she can't talk to me????