You Belong to My Heart - Nan Ryan

In Civil War–era Tennessee, a southern belle battles a cold-hearted, hot-blooded Union soldier in this romance from a USA Today–bestselling author.
She was a pampered blue blood from a powerful southern family. He was the son of a seamstress from the mud flats south of Memphis. They were born to be enemies, but Mary Ellen Preble fell in love with Clayton Knight. On her sixteenth birthday, they consummated their passion in a night neither would ever forget. But their romantic idyll was short lived. Torn from each other by a man's vicious lies, Clay left Tennessee and Mary Ellen married a man she didn't love.
Now, as the Civil War rages, the suddenly single Tennessee belle is about to be reunited with the man she once adored because Longwood, Mary Ellen's beloved ancestral mansion, has just been seized and turned into Union headquarters. And the man leading the attack is Captain Clayton Knight, who wants her back in his bed . . . but never in his heart.
Forbidden desire reaches dazzling new heights in this poignant and passionate tale of deception, war, and star-crossed love.