The Banished Bride by Andrea Pickens

A drunken laugh, a roll of the dice… and Aurora Sprague finds herself a child bride, married in haste to a young man she’s never met to settle her father’s gaming debt. Moments after the ceremony, the new groom gallops off to the army and Aurora is banished to a remote estate, married in name only.
Years later, Alex Fenimore, now a top intelligence officer, is on a secret mission when a fiery young lady helps him escape an attack.
He has no idea of her real identity—or that the sparks of desire between them are about to ignite a dangerous passion…