Others might already be thinking this... but dump her already... you don't need to add drama and though it would be nice, you don't really need a valid reason to leave someone.
If you're not happy with her.. then that's a good enough reason. The worse thing you can do is waste each others time on a relationship that goes no where.
It's clear that you don't trust her... without trust, you'll eventually lose respect for her... and then without respect your love for her will fade. I'd say, leave now before you hurt her even more...
"The weakest soul, knowing its own weakness, and believing this truth that strength can only be developed by effort and practice, will, thus believing, at once begin to exert itself, and, adding effort to effort, patience to patience, and strength to strength, will never cease to develop, and will at last grow divinely strong."
- James Allen