I like Hootie's idea.
You say you've talked to her and she doesn't get it, so it sounds like she is REALLY rude and just doesn't give a crap about anybody else. I mean, who doesn't get that at 3 am people are trying to sleep? If nothing else works, do you have an RA who could help you or something? I'm not all about tattling on people, but I don't know what else you can do at this point. Anyway, consideration to others is really something this woman should learn before she graduates from college.
The thing I've always wondered about earplugs -- doesn't it really muffle the sound of your alarm going off in the morning? I'd sleep right through my alarm if I had earplugs on, and they always make me feel claustrophobic. It might be worth trying, but I really think that the principle of the thing is important here -- you shouldn't HAVE to wear earplugs because some snotty brat next door can't keep her voice down in the middle of the night. That would really piss me off!