best NOT to assume that the poster might have forced the MiL to have the poster's mom stay at the place.
in all possibility, the MiL could have been the one who suggested that the poster's mom stay at the home. we do not know what happened that the two GMs were in the same home. best to assume that the MiL was at first suggesting that the poster's mom stay there as a gesture of possible kindness.
I do agree that the poster should with her DH and DD move out of the MiL's place.