Kirk--I've been feeling bad for what your going through. One of my sad thoughts has been this: don't Mo's reasons strike you as the kind of translucent reasons people give when they don't want to tell you the real reason? I'm thinking of the "Harry Met Sally" scene with Billy Crystal and Bruno Kirby at the baseball game. Does Mr. Zero know?
A friend of mine had his wife leave him. She said the that she was feeling she missed out by never having lived alone for any significant time. It turned out she was just falling in love with her girlfriend. It all worked out real amicably. Me on the other hand, after I got dumped by someone that I wasn't even married to, went on a blinder that lasted years. (Blinder being aussie for drinking binge) Not that I'm recommending that for you. Guess it was just my way of coping without coping. I hate to say it wasn't bad actually. I rather enjoyed it. I'm almost disappointed I didn't come out of it with a life lesson. I emerged from my blinder with a much better job, a wife, and a flat on the beach. (shrugs) It's like in the that Simpsons episode: "there's no moral to the story, it's just a bunch of stuff that happens."
Kirk, analyze not overmuch!
Accept. (yoda speak)
She has simply decided that her path goes in a different direction from yours.
There may be a million reasons why, or perhaps no reason at all.
Take a deep breath and go forward on your own way. I suspect that you will not travel alone for long.
Best wishes and good luck.