Cut her loose.
As mentioned above, some people like a challenge, some people only know what they have till its gone, and some other people want what they can't have.
You're making it way too easy for her. At this rate, best case scenario is she keeps you as a loyal back up bf, worst case is she thinks you're a complete push over and is completely put off by it.
Walk away, but don't pretend to.
You have to actually just cut her off.
You'll either find out she was the wrong girl for you or the distance will open her eyes and bring her back.
Either way you'll see the light and that is a good thing.
You can't make someone love you...