Unlike most of the people asking here, you have a legitimate question.

So I'll answer without being a bitch.

Drop her ass. She'll get over it, and as much shit as she will end up talking about you to her friends, remember, you're right and you're doing what you must to not be on the shit end of the emotional stick. There really is no other real solution. Move on or give in.

Move on to another girl if you can. That will get your message across: if she doesn't want to give you her all, someone else can have the chance.