I've found references to others having this same issue: (1, 2). It doesn't match the designed behavior reported by most of the people that play the game, and therefore appears to be a bug. It seems to only affect Xbox players.
There's no known solution or cause. It seems that you simply need to store your items somewhere else so that your greedy wife can't get to them.
Set up a man-cave.
You need to put your stuff in safe locations or containers. These are places that don't respawn, meaning that your stuff will still be there when you get back.
This includes houses you've bought such as your marital home, obviously, but also quite a few other places. I put the list in another answer, and there's also a whole question devoted to the subject.