Buy the cheapest beater bike that will get you where you are going and don't worry about it. It will be garbage after four years in the weather anyway.
My daughter is in the same situation. People buy new bikes for their kids and the university auctions off hundreds of them, abandoned at the end of every school year.
I would spend as little as possible. Graduate, get a good job and then buy a nice bike.
Large universities sometimes have a bike coop where a student can get a cheap bike.
-Tim-