Your grandmother is one among the legal heirs of yor deceased father along with your mother, you and your siblings.
She cannot be excluded from the list of legal heirs or successor in interest to succeed the estates of your father.
She is entitled to 1/4th share in the propriety left behind by your father.
She has full rights to dispose this share of property to anyone of her choice and in any manner she may decide it to be disposed.
If she is willing to relinquish her rights in the property in your favor, she may execute a registered release deed.
Nobody can object to this act or transaction she may be ready to do it.