First, make sure all your property and assets are secure, hopefully you don't have complicated arrangements like a shared lease or a shared credit card or bank account. Get that taken care of first.

Second, don't play games, don't let a doomed situation linger on, don't do "paybacks", don't stoop to her manipulative level. If it's over then it's over, break up with her by phone, and not in person, imho phone is better than letter because you know she hears it from the horses mouth, don't be vile either, just say you are breaking up because it's not yours and you can prove it, and that's it. Don't be some place she can find you for awhile, in case she looses it.