Sister fraudulently taking over the property

We are 4 sisters. Our father passed away 15 years back. My mother is not very educated and was unable to handle the affairs so we decided to transfer the property on our youngest sister's name who was staying with our mother at that time and was unmarried. We had promised each other to split the property later in life when our mother would be no more. Rest of us were married in different cities that's why we thought it will be better if one person can overlook everything. 3 of us, agreed to this whereas my eldest sister was against this. The transfer was done in the presence of we 3 sisters and our mother but without a signature or acceptance of my eldest sister. A couple of weeks back, my mother passed away and now there is a dispute. My younger sister has denied giving us our share. Moreover, my eldest sister is filing a case, as she had not accepted the deed signed and she had her objections with it. She is accusing us of unlawfully stealing her share in our parent's property. Now I am also against my youngest sister as she is denying us our share. Is the transfer valid because my eldest sister did not sign the transfer deed? Can we retract our deed now? We are Marwadi Hindus and all of us are married now.