Is the will valid if property mentioned was sold prior to death?

My mother and myself were joint owners of a flat in Mumbai since 2006. My mother made a will in 2007 bequeathing 2/3rd of her 50% share to my sister. The property was sold in 2010 while my mother was still alive. There was no will made after that and my mother did not keep aside anything for my sister as the monies received from sale of flat were spent on property purchase and other expenses. My mother died a few months back (in 2016). My sister is now demanding her share. What is she entitled to? Is there any validity on the will for property / share that was sold during the lifetime?