just do it, ask her out, forget what she thinks, what other people think, if they make fun of you, punch them or something. but trust me you dont want to chicken out, i have chickened out before when i had a chance, it still hurts to this day that i had that chance but i didnt ask her. any way, just walk up and tell her how you feel, if your friend wants to belittle you or whatnot, smack your friend accross the face and yell "BITCH SLAPPED" (trust me people think its funny, it will score you a few points with the people around you).
NOW ASK HER