Black Pansy by Suellen Ocean

At the birth of the Civil War, Scots-Irish Mabel McCrutchon is ready for love, but because her skin color reveals the family's secret black ancestry, Mabel is ridiculed in public and her own mother excludes her from social gatherings. When wealthy Abolitionist, Charles Churchill invites her to travel to New Orleans to pose as the mother of black children and lead them to safety in the north, he worries about the risk. If his scheme is discovered, Mabel will be swept into Louisiana's slave trade. After arriving at the decaying, antebellum St Francis Plantation to retrieve the children, they're greeted by a sultry blonde who knows Charles much too well.