Maternal property issue

Sir My mother and her elder sister are only two sisters.both are married.they have no real mother residing with their parents for last 25 maternal parents have written a vasiyatnama in which my Nana has stated about home in which they are living with her little daughter that i name that home to my little daughter in which my elder daughter have no concern.and rest all my property will be divided equally between my the problem is that the home in which my mother (little daughter) is living that area is very big .only we have covered half of them on which our home is Mossi wants that half uncovered field that is along with home and there is only one way to reach that uncovered field that is our Home entrance gate..and she wants 12 feet space from our gate to reach their field which she wants to take.but I wanna to know that can she authorise to take that much way from front..or can she break our home boundary by legally or illegally.. Plz suggest me becoz I m too much tensed..