Immovable property dispute between my mother and my bhabhi

I am Nutan. My deceased father had booked a plot in Rohini in 1980 in the name of my brother. My father also owned a self aquired house in north Delhi. Both my father and brother are no more leaving behind my ageing mother, myself, my younger sister, my bhabhi and my two niece both of whom are married now. My father had made a will in favour of my mother before his death. My mother and my bhabhi are living together in this house from the last 36 years but my bhabhi is neither allowing my mother to sell this property nor is she allowing her to carry out any repair/renovation. They both are not pulling along well. My bhabhi is pressurizing my mother for 1/3 rd undivided share in this property through gift deed. DDA wants NOC From my mother for rohini plot but My bhabhi is not persuing this matter any further. What should we do.