Don't pass a note!! That (next to texting) is the worst way to ask a girl out. It isn't personal. The next time you see her before practice, just say "hey. So do you have plans Friday night? I was wondering if you wanted to go to a movie or something" And if she rejects you then don't say "oh ok. Well I just meant as friends" I know it will be tempting but don't. And if she is smiling at you a lot and whatever, then it probably means she likes you. That's in my opinion. I'm a 15 year old girl and that's what I would do. Hope this helped!
DO IT. What is the point of life without best friends? Or, in your case, girlfriends. And girls don't really just smile. Only sometimes. So, she must like you. And, maybe if she rejects she will know that you like her and start to like you back.