Share in self acquired property of my father

My father acquired one ground property and built 700 sq.ft house from his own funds. We don't have any ancestral property. My father gave 1/2 UDS of land through a settlement deed to get loan from bank to build on the top of existing house. He confirmed his permission to build through the settlement deed. Now he has control over 1/2 UDS land and 700 sq.feet house. I have a sister who is married. Now my father wants to settle the rest of the property to me. But he does not want to go with a settlement deed, instead write a will, stating that the rest of the land and property will be acquired by me and he will be giving 25 lakhs to my sister. The money will be given to her in installments as we dont have huge cash to part with. The WILL will state that the property will come to me after giving away 25 lakhs to my sister, if my father is not able to pay in his life time, and after my father and mothers demise. Kindly let me know whether my sister can contest the WILL to get hold on the share?