"break up break" help please!?

My girlfriend of 2 years wants to take a "break up break" and she says shes going to come back to me after she sorts a few family things out. and also were not going to change Facebook and she still has almost 1 grand worth of jewelry that i gave her. (which i would get back if it was permanent) so i asked her to agree that were not aloud to see other people but she wont. and shes said multiple times that she doesn't want to cheat and me and isn't going to. but its hard to believe her when she wont agree to that. whats her thinking? why wont she agree to it?