That's some amazing work!
I must admit that I'm not exactly an authority on dollhouses, but is it common for the rooms of a dollhouse not to interconnect, by way of doors, hallways, stairways, etc.? I'm not criticizing your wife's work. I'm just wondering about the practice in general.
Yup. Just imagine all that stuff is in the half of the house that's cut away.
She's tried houses with stairs and doors, but she found it annoying to spend time on such concessions to reality, when she really just wants to get to building the furniture. You CAN build the house as real as you want, or you can just make it an excuse to do a collection of rooms. Hey, it's a hobby.