Burning Embers by Mary Lancaster

From the fires of war, a new hero rises.

Fifty years after Earl Malcolm MacHeth made peace with the King of Scots, the embers of rebellion remain half-hidden in Ross, ready to be ignited by ambition and resentment.
From childhood, Affrica MacHeth has adored Ferchar, the son of a local priest. Complicated and clever, fun-loving and ambitious, Ferchar secretly becomes the center of her world, and a rare bond forms between them.
But a path to happiness seems impossible. Family, war and rebellion get in the way. And when the last MacHeth rising against the King of Scots is led by her cousin, it is Ferchar, relentlessly loyal to the king, who leads the army against him.

Ferchar would die to protect Affrica, but is love or ambition behind his offer of marriage? And when it matters most, can Affrica really choose Ferchar over her family?