Why is this girl always mean to me?

I've asked out about 30 girls in my life and they all said no so I did not expect her to be any different but I hoped that she'd say yes. I have had a crush on this girl since the 7th grade and we just graduated high school. Last week I saw her at her work and I asked her out when I was paying for my stuff. She laughed and was like ewwww no way you ugly loser. I saw her a few times since then and she runs up to me and laughs and her friends call me and facebook message me asking me out as a joke. Since when is it a crime to ask a girl out? She knows I never been on a date before and she always says stuff like are you gay and stuff like that? She could have been nice to me when she said no. We're 17.