Under the Champagne Moon by Alina K. Field

Orphaned by the French Revolution and rescued by a British family, Fleur Hardouin didn’t—or wouldn’t—speak, until the jolly young Gareth Ardleigh crossed her path one summer and saved her from bullies.

Fifteen years later, Fleur and the beloved lady she serves return to Cheshire. Determined to rescue them both through an advantageous marriage, Fleur tries to brush off the attention she receives from Captain Gareth Ardleigh, who’s home from the wars and as handsome as ever. Her heart longs for him, but her head knows he can’t provide the security she needs.
Gareth’s excuse for visiting Cheshire is to deliver the personal effects of his best friend who perished at Quatre Bras. But his real purpose is finding the little French girl he met years ago, for marriage—not to him, but to the Frenchman who helped save his life.

Astonished to find that Fleur has grown into a beautiful—and still intriguing—young woman, it soon becomes clear, he must choose between honoring a promise or trying to win the hand of the woman he loves.