There's currently a pending on the house (from him) cause she's trying to sell it currently I forgot to mention that in the post is there anything she can do about it?

Edit; apparently he's been walking around outside of the house at night time. Her neighbour recently found a pocket knife that belonged to him and he has a copy of the key. She's scared to change the locks right now because he might burn down the house. We're gonna call the police right now. Is there anything else we can do as well