DD stays w/me every other week in the family home. I'm a LBS...
She basically moved out with her mother. I think that's the most self-centered thing a mother can do. Uproot the child. It's not the same to "go home" every other week.
WAW's can do this and DO do this. But if you have other "signs" that it's MLC for your wife, I'd say this is one more.
If I can let my inner redneck out for just a sec, to me, her head "just ain't right".
Only you'll know for sure.
Look to her past (specifically, her childhood) for more clues.
