That is really fine.
If your grand mother has stated in will that her daughter is not intrested to take her share,you can proceed to get the will executed and transfer the title in property.
As the word of a will deed must be specific .
If there is only this much related that she is not intrested to take her share then still i advise to get written from her that she shad relinqusihed her sahre. but if it is further mentioned that she will have no share from the property in the will then you need no other document as she is deprived of having anything from the property.