Most Helpful Girl
You have a huge advantage, you know her. Invite her out for something you know she'll enjoy doing with you. When you're out with her you just have to doe everything you can to stimulate an intimate conversation, something personal and close to the heart. From there you kinda shift things onto her, make sure that throughout this whole thing you shower her with compliments and you're kind (if you're funny make jokes, otherwise no jokes). You show her a good time and then you can make a move by asking her out on a serious date and letting her know how you feel.