Joint property sold sister received money now denying it

In 1982,i and my father registered one acre of land to my sister as pasupu/kumkuma. That one acre land has an attachment of 0.49 cents, it means no body don't buy 1 acre individually they need 1.49 acre at a time. Due that problem, in 1987 i and my father sold that property jointly to other person, in the document it was written that 49 cents equal amount is given to my father and not mentioned remaining amount was given to my sister. (Not written that amount was given to my sister) that document consists of my, my father and my sister signatures. How to prove that amount was given to mysister