Why are "coming to her senses" or "dropping out" the only options? I have a DD who is a college Jr, and she's living in an apartment this coming year. But the first two years, there were major instances of roommates doing some MAJOR partying in the city nearby (fake IDs). She had one roommate (a nursing major) that my DD frequently had to clean up after when she vomited. As far as I know, she's still a student, as are the others.
Just started typing out some of the horror stories she told me, but I'll spare you.
A bunch of them moved into a house together this year. My DD got an apartment with a girl who's pretty much not a partyer, like my DD. Don't get me wrong...I don't think either one of them NEVER drinks or attends parties but DD shares a lot with me (like all the nightmare stories from the first two years) and I feel as confident as I possibly can that she's making wise decisions. Her current roommate reminds me of the brunette in "Legally Blonde" who's the stuffy society girl (but I'm warming up to her). DD said that when the roommate gets ready to go out, she puts on pearls.
Good luck to your DD and the roommate situation. There can be a whole lot of drama.