The Highlander & the Counterfeit Queen by Heather McCollum

Bloody Hell! He abducted the wrong woman!
Daughter of a traitor, Cordelia Cranfield seeks her freedom by proving her loyalty to the English crown. Since she looks like a young version of the great Tudor queen, she agrees to stand in for her on a delicate mission. But the simple masquerade turns treacherous when a Highlander, working for the French, abducts her, thinking her the great Queen Elizabeth I.
Spy for Scotland, Marcus Ruthven has been tasked with infiltrating the French to rescue the English queen, whisking her away to Scotland so she can be thankful and name King James her heir. Marcus ignores the warning signs that this woman is too young and lovely to be Elizabeth Tudor because she’s also clever and courageous, and Marcus is desperate to succeed. They work together to evade the French as well as their growing attraction. One can’t just tup a queen no matter how good she feels in his arms.
When Cordelia is revealed, the dam she and Marcus held against their passion for one another, shatters. Missions ruined, emotions raw, they must work together now to save the real queen.
But remaining secrets surface, all masks come off, and Cordelia doesn’t know if she can trust the spy who has stolen her heart.