Wife Share in Property

Dear Sir, I had purchased a plot of land.At the time of Registration I was on good terms with my wife and so Plot was registered in Joint Name.A Loan was taken from the Bank and the Balance Amount is being paid through EMI for the last ten years from my Account.2 years back my wife said that she needed money for her kindergarden school franchisee business and took a top up Loan by mortgaging the same plot with the same Bank. As her kindergarden school business did not click and she took the proceeds from the top up Loan to settle the creditors. In the mean while I had developed differences with her relating to the way she was handling the finances and now she is sending me Legal Notices from lawyer asking to pay maintenance,Alimony and 50% share from the sale proceeds of the plot (the price for which has increased over the last ten years). She has not paid anything for the Plot and EMI.I wanted to know what are my Legal Options towars her right to claim 50% proceeds as plot is registered in Joint names(Me and wife).