Sofia has been let off her twelve-year sentence, as maid to the mayor and his wife's children, six months early, and is released to Celie's and Mr. ____'s home. Her children have barely seen her and have grown up with Squeak as their mother. The children barely recognize Sofia, and call her Miss.
The novel portrays a multitude of women. Sofia is a "strong" woman—but she is reckless with her strength, and it cost her years of her life in servitude to those she tried to resist. It cut her off from her family.
After dinner one night, Shug announces that she and Celie are leaving for Memphis, along with Grady, who is still living with Shug at Celie's house. Mr. ____ says he won't allow Celie to leave. But Celie has had enough: she talks back to Mr. ____, and says he's a terrible scoundrel who has kept Nettie's letters from her. She says she's had enough of caring for his "rotten" children and living in his home. The others at the table are completely surprised, and emboldened, by Celie's outburst.
This is another critical turning point for Celie. She has always been passive, always endured under the abuse and control directed at her from the men in her life. Now, finally, she talks back (though note how she doesn't physically fight back, as Sofia might have). Celie makes her thoughts and desires understood. She makes her voice heard, and in so doing takes control of her own life.
Celie tells Harpo, too, that he is partially responsible for Sofia's service to the mayor's family, since Sofia never would have run away from him in the first place if he hadn't tried to beat her and control her.
This is, of course, more or less true. If Harpo had not wished to control Sofia, they might have lived together happily for the intervening twelve years.
Shug announces that Squeak, too, will be going with them to Memphis, in order to try to sing professionally. Eleanor Jane, the white girl Sofia cared for, comes over at this point and interrupts the meal. Eleanor Jane asks to speak with Sofia; her family, the mayor's family, is having many problems (the younger son appears to be an alcoholic), and Sofia still helps the family out a great deal, giving Eleanor advice, even though Sofia is no longer their servant.
Squeak follows a path toward independence similar to Celie, but she needs to shepherded along by Celie and by Shug. She doesn't yet have Celie's strength. Eleanor treats Sofia like a mother, which contrasts Sofia's relationship to her own children who hardly know her. Eleanor's bond to Sofia seems to be genuine, one of love—she seems to value Sofia's ideas, rather than think of her as a servant.
After returning from talking to Eleanor Jane, Sofia says she will look after Suzie Q, Squeak's youngest child, and the other children while Squeak is in Memphis. Suzie Q. has already taken to Sofia, whom she does not know is her father's first wife.
At this point, Sofia becomes the mother to Harpo's children with Squeak. This is an interesting inversion, since Sofia is no longer recognized by her own biological children—the children she had with Harpo.