Sunflower Sisters by Martha Hall Kelly

It's 1861 and New Yorker Georgy Woolsey is training to be a nurse during the war. Meanwhile, in Maryland, slave Jemma tries to survive the brutality of everyday life in order to someday be free. She is owned by self-centered snuff addict Anne-May, mistress of the Peeler Plantation. Sunflower Sisters tells the stories of these three women throughout the Civil War as their lives intersect. The Woolsey sisters (of which there are six) are the ancestors of Caroline Ferriday, the main character of Kelly's novel Lilac Girls.