WOW, tank... I do not think I'm equipped for this type of support... I have a shoulder if you need to cry, though...
Joking aside, I do not want to jinx this for you.
The only advice I can offer at this time is move slowly. Think about what you want. Have no expectations. Don't get too excited, she hasn't moved in yet.
I know you are shocked. Is there anything or things that you can think of that might have lead her to this decision? Is she liking you, is she regretting her choice to leave, her life sux, she just seems more... clear minded...?
I would also suggest "more of the same". Whatever you have been doing HAS BEEN WORKING. Don't start reverting to past behaviours or making any drastic 180s at this point in time...
And good luck. I'll be putting out the prayers for you tonight, man!