How can I make sure a will is Not Contested in Horry County, South Carolina? Re: money left to grandchild who was not legally adopted?

My mother-in-law (an elderly widow) has just written her will and is leaving her money to her five grandchildren (who are all adults). She told me the will states the words "To My Grandchildren" and specifies the names of each of them. What she neglected to tell the attorney is that her eldest "Grandchild" was never legally adopted. I am afraid some of her children and one of the grandchildren may contest the Will on this technically if they become aware of the wording. I have already told her to speak to her attorney about this, but I doubt she do so without the permission of her daughter, with whom she lives. Her daughter is aware of the lack of adoption and was present when the will was written, but suspiciously neglected to mention this to the attorney. What can happen if she does not have the word "Grandchildren" removed from the wording?