Looking for a book title/author

My sister is looking for a book that she read maybe 10 years ago. It was set in the 1980's in the U.S. The main characters are an inter-racial couple. The woman, who is African-American, is sent back in time to pre 1865. Her man goes back to rescue her and return her to the current time. If anyone can help, please post the answer to Debber5. Thank you in advance for any help you can give.