Transfer of property

Hello, me and my Ex Sister in Law have invested in Apartment property in Pune back in 2008. We invested 38 L back then and now current market price is 85 L. My mother funded the investment for both of us. Since bought; that property is on rental. My mother takes rent who is more than 70 years old. My Sister in Law name is primary and my name as secondary in join. This property was bought when she was married to my elder brother. They have one daughter who is now 24 years old. However, in 2017 she divorced and legally separated. Daughter stays with her mother. Now my Sis in Law is married again to some one in 2020. When property was bought I was Indian citizen, but in 2018 I became US citizen. I have my POA with my Brother in Law. Now we want to sell this property. My ex Sister in Law has no problem for that "so far". However, after selling the real estate property she and I agreed to transfer the money my mother since my mother funded this investment. My mother wants to invest that money in some monthly or quarterly Government scheme which will give her monthly or quarterly basis regular income. However, after her remarriage my Mother don't have much trust in her Ex daughter in Law. She wants to get property sell as quickly as possible. Also finding and managing tenant is not good option for my mother. However due to Covid 19, we have decided to postpone sale in 2021. 1) How my Ex Sister in Law and I can gift deed to my mother ? Since I am in blood relation may be I can but how can she do it ? 2) Do we have to pay any stamp duty in Gift deed ? 3) As 2nd option, Can we transfer my Ex Sister in Law's share of property in my Mother's name ? so my mother and I will be joint holder of property. In this option; I think we have to pay Stamp duty and registration fee per current Ready Reckoner rate in that area. We will reimburse Ex Sis In law for that. We can take advantage of reduced stamp duty from 5% to 3% till March 2021 by Maharashtra Government . This is little expensive option. 4) As 3rd option, Can my Ex Sis in Law gift deed to her daughter and can her daughter later Gift deed to her Grandmother i.e. my mother ? This way we can avoid paying Stamp duty unnecessary. Pls advise which option is better and legal.