The Ghost Who Cleans

My daughter called me about 11:15 tonight to report that my grandson is telling her that there is a Momo (grand mother figure) in his room. When ask what she is doing he replies that she is cleaning. He was upset and asking to sleep with mom (daughter)
I told her to have him tell the lady to GO AWAY. She said she did but he was still upset. I had her put him on the phone with me, and I asked him what was wrong. He was crying and said " There is a Momo in my bedroom". I told him TELL HER TO GO AWAY..Ok he sniffled cried harder. My daughter then took the phone and said bye. It's been an hour and she hasn't called back. Either the Momo went away, or he fell asleep crying. It has really un-nerved me to think that he sees these "things". I'm thinking of nailing a cross/and or a pentacle above his door.
It's just down right creepy, besides I don't know why she is haunting him. My house is the one that needs cleaning. My daughter keeps a spotless house.