Property Dispute

Hi I am living in Vasai , Thane in my grandfathers house. I Live with my mother and wife now. My grandfather brought this property in 90's and since me and my father were not in mumbai He included one of His daughters name in the agreement (My Aunt ). Now my grandfather passed away but before he passed away He wrote his last will. In the will it is mentioned that her daughter ( My aunt ) has no share in the property as she has not invested anything or taken care of him. According to His will the propery belongs to me and my mother. Now we need to move in a better place and want to sell the property my Aunt has been dragging this issues from 4 -5 years . We gave her the option of Gift deed but its just been draging. Few quick questions. The Flat Agreement has my Aunts name but according to the last will which is the last legal documents my grandfather has cancelled all her rights over the property. Do i still need to get a gift deed done from my aunt ? According to the will the property should have been transfered in to my moms and my name but the socity says they need the letter from the aunt. Is there any way out ? Please suggest the best way to sort this out. as i and my mother have been living in the propery from past 18-20 years.