How is Madelyn Farley an important character in the novel, Father Melancholy's Daughter?

Margaret disliked Madelyn Farley the moment she arrived at the Gower household, carrying a strange granolatype energy food. When Ruth leaves with her — as fate would have it, to never come back — Madelyn becomes Margaret's unseen enemy for the rest of her childhood. It is not until after Walter's death that Margaret finally meets her again.

This results in the most dramatic reversal of the book. While in some ways Madelyn is just as Margaret remembered her — loud and tactless, lacking the grace of Southern women — she no longer appears an ogre. Margaret discovers her to be a vulnerable human being, devoted to her friends and her art, and even bearing love and guilt toward her dead friend's daughter. She ends up touring with Margaret as a surrogate mother, at a time when the younger woman needs it most.