fathers niece filed injunction on ancestral property

my father got property after release or partition deed in the year 1975 (registered) from his brother, sister in law and mother. My father has sold most of the property during 1993-1999, remaining property was transferred to my mother during 2004. recently, we are planning to sell the property, my niece (father's brother daughter) has filed a case against to give share from the remaining land. She claims that the property is was sold by father on behalf my niece father. But she has no document for her claims, she produced family tree and taken temporary injection order against the selling. Please give your valuable suggestions, to fight against the same and to close this case.