Beloved Enemy by Rebecca Ruger

Charlotte O’Rourke, a lonely kindergarten teacher in 21st century Florida, travels to Scotland on a whim, seeking adventure and a break from her mundane existence. When an ancient amulet purchased at a curious gift shop thrusts her back to 1302, she finds herself in the midst of a brutal war between the Scots and the English, not exactly the adventure she’d been hoping for!
Captured by Reid Nicholson, a fierce laird who has been betrayed in love and hardened by war, Charlotte’s striking but strange appearance and her mysterious amulet arouse suspicion, persuading him to believe her a spy. Despite his certainty that she is the enemy, Reid is reluctantly drawn to Charlotte’s resilient spirit.

As Charlotte anxiously fumbles along in this perilous new world, she is increasingly intrigued by the laird of the Nicholsons. Together, they face treachery and confront their own deepest fears about love.