When I was pregnant with my second I could not get off the couch in the end. Maybe, you can let the housework go for awhile before the baby comes and let MIL take care of it when she comes. I wish I had had that really. The moving things around- just put them back when she leaves and the house is all clean.
The thing that might bother me is if she were an awful cleaner, like scrubbing the finish off the sink or the paint off the wall!