Why don't you make it simple and say "Hi, who are you, in which class are you..." etc, etc. Just talk casually, be interested in her, and do drop some information about you so that your communication remains even.
Basically the goal of your information would be to get to know her better, and to find out opportunities to meet her again (is she routinely at the library? what kind of activities does she like to do, etc).
Just do things the simple way, and only think about complicating it when the simple approach is not sufficient.