I need some girl advice?

I really like this girl at my school. I told her how I felt about a month ago and I thought she felt the same way too. I was going to ask her out but my friend said I shouldn't. He said that I should wait a little bit. Then he said that he liked her and that she said she didn't like me. Being the gullible idiot I am I believed him. I pretty sure she likes me but I still have that feeling that I'm wrong and If I ask her out she will reject me.The last two weeks every time I see her she is looking at me and smiling.The other day I was playing basketball with some friends and I look over to the bleachers and she is staring at me. I looked over a lot and she was still looking at me. I want to ask her out tomorrow because after tomorrow we go on thanksgiving break. I just need some advice that could help her say yes. I know that she likes me but I'm very shy and I don't want to be rejected.