She is portrayed by Sigourney Weaver.
Her grandfather, Charles “Trout” Walker, made her dig holes to search for Kissin' Kate Barlow's treasure when she was a child, even during Christmas. This caused her to become bitter and just as obsessed with the treasure as he was. Her henchmen are Mr. Sir & Mr. Pendanski.
After Trout died, she opened a delinquent camp for boys in hopes to find it faster until Stanley Yelnats IV found the treasure with his friend Hector Zeroni. Walker was ready to claim it as her property, but the chest it was kept in had the name of the first Stanley Yelnats, and so the entire fortune was given to the Yelnats family. Also, as though a curse had been broken, the rain to finally fell after almost hundred years.