Who is Miss Margaret Treasure from Meridian: A Novel and what is their importance?

Margaret Treasure is an elderly, obese black woman who lives on a family farm and rarely has contact with anyone but her sister. One day, when her house is being painted, she falls in love with one of the painters and begins a sexual affair with him, though he is over twenty years younger than she is. Margret believes that she is pregnant and burns down her corn crops and her bed. When she injures her leg, Truman and Meridian bring Margaret to a doctor, who also is able to tell her that she's not pregnant. Margaret is so happy that she agrees to register to vote.