Lady Belling's Secret (The Secret Series #1)
Amylynn Bright

Unfortunately, mail is slow during a war. She thought he knew everything. He had never suspected.
Thomas has always wanted to be a part of the Bellings family but he was too foolish to grab the chance when she threw herself at him before. Instead, he ran off to war. Emboldened by his new-found appreciation for a grown-up Francesca, he finds that dream is within his reach.
If she thinks he’s running away this time, she has no idea what she’s in for.