This act was deeply symbolic on so many levels!
Women - especially women of color - in those days had to fight so hard to have any power or any voice at all. Because they had been "property" for so long, they were seen as less than human. The gendered power structure in this book in particular felt overwhelming - from the women at the factory to the women in each home.
The greater tragedy of Nan's loss was compounded by the fact that the act was committed by her own mother, who instead of helping her, handicapped her in a way that hurt her for the rest of her life. So this act causes us to consider what effects our mother's actions have upon our lives. How to they help us? How do they hurt us? Ketty thought she was protecting her daughter from getting tongue cancer, but at what cost?