Dude,
So it has taken you 1.5 years to work up the courage to talk to this girl where it should have taken 3 seconds.
"How much did your math book cost" is the type of question that will most likely get a one worded answer. Why do you care how much her book cost???
If you have known her for 1.5 years, surely you know a little about her. Her interests, where she hangs out, what she studies, etc... Come on!!! you can do better than that!
The trouble is that you are looking for a quick and easy way of getting this chick. Well there are no shortcuts in this game my man. I am not sure how much you have read up on this site, but you only have 16 posts to your name. So my guess is that your "game" isn't so advanced.
It is natural to feel the way you do. Nervous. You dont know what to do. A slight one-itis situation, and so on and so on...
Some of the guys on this forum who you see picking up women on demand and f-closing very hot HBs on a regular basis were in your shoes one day. Read the bible, go out and talk to women! Practice, practice, practice!!!
Then you wont even be asking us what you SHOULD be doing, but telling us how you manage to sweep her off her feet without breaking a sweat!