Whether the land was earlier allotted to your father. As if you have received the occupancy rights or ownership rights after your dads death and your dad was not having the same. The first question is whether the said land is termed as your self acquired property or only occupancy rights is given. If only occupancy rights are given sister can't claim the same. As the said land was never of owneerhip nature to your dad the rights of your sister can't be established in the same