If she knew that you hated him, do this; Tell her face to face that you are done with her, because of her dishonesty. Make it blunt as fuck, and at the end of it don't wait for a reaction even, just walk away.
If she didn't know; Tell her you're tired of the dishonesty, and that you don't know what else she may be hiding, or lieing about. Break it off, by the sounds of it there's better girls out there anyways.