how significant is it that sofia ends up as a maid in a white family

A good answer to this question will look deeply into Sofia's character. She is a fighter and seems more independent than Celie, but her journey is far less significant than that of Nettie. Consider also Sofia's relationships with her own family members as well as the portrayal of the white community in conjunction with the black community in Sofia's place and time.

Since Sophia is a strong character and was steadfast against being the Mayor's maid, I think Ms Walker (writer) was proving the point that back then eventhough you may be black and strong willed, the white folk still had the power and control over you to have you do things that you didnt want to do normally. it was a lesson in where the power lies.