Peggy is Paul Truman's wife. She is Will's sister-in-law and daughter-in-law of George and Marilyn.
As Peggy appears only in one scene, and is not mentioned in other episodes, little is known about her, other than she is wary of Grace being around her husband because of her history with Sam, Will's other brother. She also innocently makes antisemitic remarks, implying a conservative upbringing.