Who is Mama Dabney from Return from Tomorrow and what is their importance?

Mama Dabney is George's grandmother. She cared for George and Mary Jane while their father was out of town on business. George remembers how Mama Dabney loved her wood stove, as well as the cows and chickens she kept in the yard. He notes that he woke every morning of his early life to the sound of her "beating batter bread" as part of the breakfast preparations.