A Most Inconvenient Marriage, Ozark Mountain Romance Series by Regina Jennings and published by Bethany House Publishers.
Having fled a difficult home life, Civil War nurse Abigail Stuart feels like her only friend in the world is sweet but gravely wounded patient Jeremiah Calhoun. Fearing he won't survive, the Confederate soldier's last wish is that Abigail look after his sickly sister at home. Marry him, return to his horse farm, and it'll be hers.
Left with few choices, Abigail takes him up on his offer and moves to Missouri after his death, but just as the family learns to accept her, the real Jeremiah Calhoun appears puzzled to find a confounding woman posing as his wife. Jeremiah is determined to have his life back to how it was before the war, but his own wounds limit what he can do on his own. Still not fully convinced Abigail isn't duping him, he's left with no choice but to let the woman stay and help--not admitting to himself she may provide the healing his entire family needs.