Will based on disparity

Sir My grandmother owns a property (land), where my father and his brother are living. my father took loan and used a part of his salary to construct the house in 1990s. We are a joint family and all of us have very good relations. I am the adopted child of elder son, adopted from younger son (I got to know in 5th standard, but no one knows I know). We are 3 children in the family 2 daughter and 1 son. My grandmother has always discriminated between male and female since we were kids. She never liked my mom as one can understand the psych. She and my late grandfather live with us on ground floor since we made this house. Grandfather died of cancer few years back. I have always loved her and given her right advice irrespective what she has done to me and my mom. She has always kept my father by her side through persuading talks (as he had a past history of depression and we had very bad time taking care of him). Now, its been some time that she is dividing her savings, in the ratio 15:5:1 i.e grandson, granddaughter, me (even from my and her joint post office savings a/c). Me & my mom are broken emotionally, no one is from my side to say what injustice she is doing. I am saying it now because it's very visible (her emotional tortures could not be proved, but this can be). I love my joint family but no one is saying anything. I am married. I am sure she will give this property to her grandson. Is there anyway I can stop her or challenge her will later if she make(/made) one. Do I have any legal right in this case.