I'm sorry, Mike. I wish I had something to say that would make it even a bit better, but truly.. I have nothing.

First thoughts.. it sounds like something she was planning to do, not a spur-of-the-moment thing. See if she'll come over and talk to you, or at a neutral location, or over the phone as a last option. In my opinion, she owes you an explanation at the very least. If you can do your best to just listen, rather than try and have a discussion while she's talking, it might give you some insight at least. If she was thinking about it beforehand, she probably has a rational (maybe not to you but at least to her) reason for leaving.

Good luck.. i'll be hoping (and praying) for the three of you.