The Invention of Wings by Sue Monk Kidd (2014) Viking 

Sarah Grimke, living in pre-Civil War Charleston, is given Handful, a slave, to be her handmaiden.  Sarah doesn’t want a slave, but she is given no choice.  Over the next thirty-five years as the girls get closer and Handful looks for a way to freedom, Sarah and her younger sister, Angelina, go north to help with abolition and women’s rights.