Who is Magnolia from My Louisiana Sky and what is their importance?

Magnolia is Dorie's African-American cook and housekeeper. After Granny's death, Dorie Kay sends Magnolia to Saitter to help at the Parker's home. Magnolia reminds Tiger of Granny. At the Parker home, Magnolia is kind and thoughtful with Corrina, and with Magnolia's encouragement, Corrina changes out of her dirty nightgown and bathes.