She is portrayed by Melinda Clarke.
Grace was a waitress in a diner that Elijah frequented after the death of his mother. Sensing Elijah's weakness, Grace manipulated him into falling in love with her and she and her two children went to live with Elijah at his mansion. Eventually, Grace and Elijah married.
Seeing him as a competitor to the vast Van Dahl fortune, Grace and her children are more than unhappy when Elijah brings Oswald Cobblepot, his son and only blood-relative, to the mansion. Although they hate Oswald, they feign acceptance.
While Oswald and Elijah talk, Grace overhears them. She hears Cobblepot confessing that he has done bad things and then interrupts the two, giving Elijah what is supposed to be medicine for his heart. However, she is later shown to swap Elijah's medicine with peppermints, most likely in the intention to kill him in what seems to be an accident to inherit his fortune. Grace and her children approach Elijah and Oswald the next day, having researched Cobblepot and found out about his criminal past. Grace reveals this to Elijah, hoping that he would throw Oswald out of the house. Unbeknownst to her, Oswald had already confessed to this and Elijah had forgiven him for all his sins, so Elijah's reaction is not at all what she expected. After their plan has failed, Grace sends her daughter to seduce Oswald to find out what he has planned for the "Old Man", but that too fails.
After Elijah has a heart attack due to Grace's botching with the medicine, Grace sends her children to "clean up the mess" and to call for an ambulance. The doctor reveals to the family that Elijah does not have enough time to live, but Elijah disagrees. Nonetheless, he tells his wife to call for their lawyer to get his affairs in order. After she has done this, Grace tells her children about Elijah's intention to change his will and tells them that they have to get rid of Oswald. She later poisons Oswald's drink but Elijah drinks it and dies, much to the supposed shock of Grace. To get rid of the evidence, Grace's son spills the rest of the drink.
After Elijah's funeral Grace at first tries to throw Oswald out of the house but decides to keep him as a servant until they will ultimately kill him, making it look like a suicide. Although her children are more than unhappy, Grace tells they need to keep Oswald close because with the right lawyer he might cause them trouble. Indeed, the family holds Oswald as a slavelike servant, misusing him on every oppurtunity. During his work for Grace, Oswald finds the flask used by Grace to murder Elijah. Having grown suspicious, he smells at it and uses it to pour some water to Grace's dog. After seeing the dog dying with the same symptoms Elijah showed, Oswald realises what Grace did and laughs manically.
While Oswald serves Grace her dinner, she finds fault in the consisty of the meat and tells Oswald to ring the bell again, as her children have not yet joined her for dinner. Oswald angrily reveals that he knows about the poison that Grace used to kill Elijah. He also reveals that he killed Grace's children as retribution against their abusive behavior towards him and made food out of their bodies, presenting them as the meal that Grace was eating. Realizing that she was eating her dead children, Grace is wrecked with complete guilt and horror, and Oswald brutally stabs Grace to death, avenging his father's death. He would later use Grace's severed head as decoration.