If she's not working or going to school this summer, is she willing to even things up some other way? I'm thinking could she be the stay-at-home partner who does all of the house chores- cooking, cleaning, laundry, etc. while you work full-time? At least until she has classes again? Maybe then you would not feel so resentful. Or does she just think everything is owed to her? Money and division of chores are two of the most common things couples fight about. Adults realize that for a relationship to work, both partners need to make some effort in one or both areas. If she's not at a point in her life where she understands that, then maybe she is not ready for an adult relationship. It might be unpleasant for her to hear you make the request, but it's a serious issue that needs to be discussed and addressed. Otherwise, you'll continue to grow more resentful and things will get worse. If she's not willing to compromise on the issue, then it's best to end things.
“This planet has - or rather had - a problem, which was this: most of the people living on it were unhappy for pretty much of the time. Many solutions were suggested for this problem, but most of these were largely concerned with the movement of small green pieces of paper, which was odd because on the whole it wasn't the small green pieces of paper that were unhappy.” ― Douglas Adams, The Hitchhiker's Guide to the Galaxy