Frack,
Wow, dude, I didn't know you're twenty! I'm don't think she'll call right now. Up til now, she didn't see you that way for whatever reason...age, thought you were outa her league. What you'll probably have to do is see her a couple of times either at work or at that gym again (I know you don't like that gym now) to establish a little more of a "friendship", then ask her to meet you for a drink or something and you'll probably be doing her that night after she has a couple of drinks!
Good job asking her out. I think most of us miss out on so many opportunities because we don't think they'll pan out!