Daughter's demand is it valid.. how to resolve.

Dear Legal experts, Please give your guidance for the following issue.. ( Staying in Tamil Nadu ) My father passed away in the year. 1970, I have my mother aged 82, and 4 sisters, all get married / settled well, My mother supported family with Agri Land, Land records "Patta" and all the ownership shows she is the Owner of the Land, 4 years before My mother given Gift settlement deed registered on my name. Then after I changed ownership of land on my name. My all 4 sisters got married before 1985, To avoid disputes at later stage I got Release deed from all my 4 sisters & duly Registered . I consider Now I am only absolute owner the Land & It is considered as Self earned.. I have authority to sale the Land to any one.. Now I wish to understand what should be my only daughter’s rights on the land.. , She is now aged 18 running, ( Not yet completed age 18 )j, If I wish to sale, Is it My daughter’s signature needed..?, she is demanding 1/2 of the land ( 50% ) share on the land, Last 7 years my daughter and her mother ( my wife ), staying separately due to some mis-understanding, My mother and myself staying alone. I need urgent fund for my mother's hospital bills. . What should be my legal rights for Sale, ? and What should be my daughter's legal rights. Potential buyer ready to BUY the Land.. but my wife file court case demanding 50% share of my daughter’s rights saying my wife is guardian of my daughter. Court didn’t even take this case for listing, Last 4 years passed.. Nothing is moving, Every day getting frustrated .. what is the legal possibility. Pl. kindly suggest. Note : No Divorce case pending. .... Thanks in advance for your guidance. Best Regards, Anandan.R