Didn't know about the other girl who entered her daughter's body. And if they knew that Cattarina's soul was not in her body. What did they think they will do to Cattarina's body, which only left its shell and has been filled with other souls from another world as well?
This kind of imaginary image made it quite difficult for Monna to accept it. If it were true her whole identity would be known. Where the Cattarina family also couldn't possibly know if she didn't tell anything.
Because most of Cattarina's memories were still left in her body. So that Monna can remember and absorb all of her memories properly. As if that memory was also part of her.
Going through it and experiencing it for herself, like being completely immersed in her brain. So that sometimes Monna also felt that she was another part of Cattarina. Split in another world apart from the soul of the owner of the body.