Legal ways to prevent selling of property by mother under influence

We are 2 sister and no brother. My father demise in year 1997 and all my father property turn to my mother's name. My mother made her first and last will in which she state equall share to both sister. My husband build pakka house for her and bear all expenses of my sisters daughters marriage. Till date all farm product are used by my sister because she takes care of my mother and I help her financially bcoz I have my own family. Now my sister another marriage is going to take place in next year for which she is influencin my mom to sell her property to help her in marriage. How can I stop my mother from selling her proper ty? Her age is 78. And she is not physically well nor even she can walk. She is in bed and my sister is trying to get profit of her situation. Please help what I can do in such situation. Thanks for reading.