I have taken 2,00,000 Loan amount @12% per month

I have taken 2,00,000 Loan amount through hand cash at the rate of 12% Interest per month on my firm name and i have paid rs 1,20,000 towards interest to my private money lender by transfering into her bank account only, my money lender has forced me to change 12% interest into 12% Profit per month i.e is 24,000 which is clearly in the agreement, we both named the agreement as Investor's Agreement. Agreement is in Printed form in Letter-pad of my firm with two witness. Agreement period started in June 2015 ended in 10th May 2016, due to loss in my business i had to close my shop permanently and i intimated her my new address through registered post , from past 6 months my earning capacity is decreased now i'm not able to repay principle amount to my lender, she is threatening me through calls, visiting my home, i have explained her to give me some time to repay the amount but she is not listening. she is not a registered money lender and when taking loan i tried to negotiate with the interest rate with her but she never decreased the interest rate.i'm sincere and i wanted to repay her amount but i need time, i wanted to send her a notice stating that i will repay the amount in 36 monthly installments which is 3 years with an annual interest rate of 18% per annum. please suggest me a better solution.