Advice regarding family dispute over the ancestral property

Dear Sir, Please suggest on the below issue: The property was purchased by Mother and Daughter in a share of 50-50, and after some time mother has made a gift deed of her share in favor of her daughter, now her sons are claiming that the property belongs to mother and it should be divided among all Children. Although they are not aware of the Property location and all, but now they are saying that they will get the property papers from Court. The daughter is very afraid because she is alone her husband is died and the land was bought from her hard earn money. Kindly suggest us what precautions she should take. Thanks.