Before meeting Isaiah, Grace was married once before to an unknown man and later widowed. She worked in the Walnut Grove post office when she met Isaiah. The two started becoming friends and when their relationship started growing, Isaiah was too shy to ask her out but eventually did and the two began a courtship. (Episode 206: The Spring Dance)
When Julia Sanderson died and the issue of the adoption of her children came up, Isaiah and Grace finally got married and adopted the Sanderson children John, Alicia, and Carl. Their life was good. She supported him as a good and loving wife but their marriage was difficult at times as she had to frequently stop him from getting into trouble and intervene when it came to the children on many occasions. They were all good friends with the Ingalls family and traveled to gold country after their crops were destroyed by heavy rain. (Episode 321: Gold Country (Part 1), (Episode 322: Gold Country (Part 2))
They eventually left gold country after seeing the results of the chance to become wealthy from their friends they had met there. The Edwards family didn't return to Walnut Grove like the Ingalls did, and went their own way. (Episode 322: Gold Country (Part 2) During this time, Isaiah had a successful logging empire and they and the remaining two children lived in a large house. Their fortunes changed after Isaiah was crippled for a time after saving Alicia from a falling tree. After resigning from life, Grace wrote to the Ingalls for help. Edwards did eventually recover with the help of Laura and Charles Ingalls. (Episode 608: The Return of Mr. Edwards)
Years later, Grace lived with him possibly in a more modest situation. Later, their adopted son John Jr. was murdered on the streets of Chicago (Episode 808: Chicago) and their relationship became strained as Isaiah could not cope with his son's death, and started drinking heavily, seeping into alcoholism. Soon Grace could no longer live with him and after a drunken episode that spoiled Carl's birthday party one night, Grace left Isaiah and Carl and Alicia stayed with her. Some time later, she writes Isaiah telling him that she has become involved with a man named Nathan Sims and has filed the divorce papers. She and her new husband's life was good and they lived happily thereafter. (Episode 819: A Promise to Keep) She was never seen in Walnut Grove again.
Behind the scenes
Grace was portrayed by actress Bonnie Bartlett. During an interview with Bartlett by Prairie Fans, she was asked what is was like being on Little House on the Prairie: "I adored working on Little House. Michael Landon was a wonderful boss and the whole cast was terrific. I particularly enjoyed my scenes with Melissa Gilbert who was 10 or 11 at the time. Unfortunately, we are political enemies as far Screen Actors Guild is concerned. I used to mess up with the props sometimes, being so involved in my "acting" that I'd pour coffee onto the ground instead of the cup. Michael loved mistakes like this and would laugh and tease me in front of everybody."