Is this a good way to ask this girl out?

There is this really hot girl who sits next to me in one of my cles, and she flirts with me alot (ie she sometimes tries to play footsie under my desk, etc.). Anyway, I offered to help her study for a test recently. She smiled and after finding out how long I prepared my notes to study, she politely declined and said she would just study on her own (I already knew she didnt study much, but I figured that I wanted to offer her help so she got a good grade). Anyway, she later started asking me questions about myself and so forth. At any rate, I feel good about my chances with her, and am thinking about asking her to hang out in a cafe. Should I ask her if she likes coffee and then tell her that I would like to buy her coffee sometime? Or does that sound weak, like I am being submissive to her?