The Quaker and the Rebel, Civil War Heroines Series by Mary Ellis and published by Harvest House Publishers.
Emily Harrison, a passionate anti-slavery advocate, has to give up her passion as a conductor in the Underground Railroad since her parents home went into foreclosure after they died. She now found a position as a governess in slave-holding Virginia. To further add to her distress, attractive, spoiled, yet elusive Gray Wraith lives right under the same roof with his uncle. Fortunately, she's managed to avoid him since he seems preoccupied. But Gray is not who he appears to be; he is on Emily's side as a Quaker leader of the Rebel Partisans. Will they ever trust each other enough to confide their true purpose in life and love?