well i would first suggest talking to her in person, and looking at her reactions that way. When talking to people through IM and the like you cant look at a person's body language, and see how she is really reacting to you.
Im guessing from your post your probably between the ages of 14-16 (sorry if im wrong) and i dont mean any offence by this at all, so not having gone out with someone before is nothing to worry about, and it doesnt matter if she has been out with loads of people either. So dont worry! Just go talk to her, get to know her and take it from there
good luck, let me know how it goes xx