property sale

My grandpa second mother son is my father. First mother have one daughter. After my grandpa death we discussed and fixed some land for her and my father, but not maked agreement. All patta and document in my father name, if my father sell property(as we discussed separated property) to a guy(relative),if she can make file opposite to my father.what wil be the judgment ? And what will be happen to the sold property? Note: all document in my father name, we not make any written agreement with that first wife daughter. Thank you..