Partition of property

Dearexpert, My mother has one sister. My mother's father have died since long before marraige of my mother's sister.after partition of property among brother of my mother's father,my mother's mother have been given the equal share of property( approx 30 acre land and some residential plot). all property is in the name of my mother's father. my mother's mother has registered a plot of 7 acre land in the name of my mother's sister secretely aaprox one year before. these days she (mother's mother) disclosed the fact saying that it has been done due to promise given by her (my mother's mother) on the occasion of marriage of my mother's sister whereas it is not fact. My mother's mother favors my mother's sister for the reason unknown may be under presser of my mother's sister. My mother's mother says that partition of remaining land among both sister( my mother and my mother's sister) will be done in equal share without taking into account of 7 acre land which has alreday registered in the name of my mother's sister. Whereas my mother desires to have a equal share taking into account of all land (30 acre) and in all plot. It is mentioned here that the plot which has been registered in the name of my mother's sister is very important plot. My mother wants to have a share in this plot also but my mother's sister not ready for it. Please advise me legally what will be share in favour of my mother in these situation.whether my mother can acquire the share in that plot which has been registered in the name of my mother's sister. My family belongs to Hindu family. It is clarified here that my mother's father had two brothers. all of them had acquired the 90 acre land in collective manner. My mother's father died on 1981.my mother's sister was got marriage in the joint family of my mother's father i.e. in the year of 1990-91. Partition between brothers of my mother's father and my mother's mother has been made in the year of 2000.It is mentioned that property was purchased by my mother's father in his name. My mother's mother has registered the said land (a plot of 7 acre of her share) in the name of my mother's sister in the year of 2014. sister's marriage terms was not existed in that time. It has been orally created in these days. kindly deliver your advise on the point whether my mother can file a suit for partition in the land which has already been registered in the name of my mother's sister in the year of 2014.