Property Issue

I live with my mom.. We are 3 sister's.. One is elder than me and other one is younger than me.. My father got expired 2years before.. My elder sister eloped with a very bad men.. With no class and disrespects evryone.. My father use to hate him but as after few years she gave birth to two child, my parents accepted them.. But after accepting both husband wife that is my elder sister and brother in law use to fight a lot.. And after my fathers death my my mother and i got alone so we brought them home to stay with us but with a year again they started quarreling like dogs and my mom is high pressure patient so she told them leave the house to my brother in law.. He went but along with him my sister also went but she comes at night to sleep sometimes.. She don't even talk to us.. But now she is forcing my mom to give her share.. She verbally abuse her and me using tons of abusive words... She threatens mom that she can take the property without mom's permission as its her dad's property too using law... And kick us out of our property.. Can this happen by any chance??? What can we do please suggest us.. The property is on my mom's, my, her and younger sister's name but it is not divided.. My elder sis says she is making some kind of separation papers by what she can take the property?? Is it possible without my mom's permission?? What can we do??