validity of legal claim against the will

Hi sir, My Maternal grandmother created a will to transfer the property after to my mother 11 years back and now my Granny is no more and after 10 years my aunt (mother's real sister) wanted the partition in the property and sends the legal notice. now we have the legal will which is created by grandmother and we have rented the same premises to the third party. Kindly advice the legal remedies available and the legal right of my aunt in the property as will clearly states that my mother is the sole legal heir to the property.