Something about her at the moment is just creeping me out.
I can see why. I imagine it's the sneaking around. She didn't really seem to try that hard to hide it, but I suppose she figured you wouldn't suspect if she indicated OM wasn't coming until next week. I know the feeling...a sucker punch to the gut. I know this is hard and I feel for you, but it really is up to her to make the necessary changes to make herself a suitable choice for you.
You cannot be lonely if you like the person you're alone with. Dr. Wayne Dyer