Based on my personal experience...
Giving a girl art can be a good thing, if she appreciate art. She doesn't have to be nerdy to appreciate a drawing of her, though it might be better to offer her something that you displayed in your art class and then decided to give her. Giving her a drawing of her which took you fifteen hours to do might come across as a little awkward - that's a lot of investment for a girl you haven't even gone on a date with.
You state she's not a nerd, so drawing her in a superhero comic might have been a risky bet. Especially since it shows two female characters (IIRC), and basically seems to be playing into the repressed lesbian fantasies all us men have. (Mmm... two super strong women tearing their capes off of each other... Yum.) Half of gift giving is picking something they want, not you want. If the girl you want isn't into superheroes, draw her with the cast of the
OC or
Grey's Anatomy or something.
Sorry if I'm coming across as brutal, but don't ask questions if you don't want the condescending, uninformed masses of the internet if you don't want an answer.
Don't get me wrong - I applaud your efforts and wish you all the best.