Book 4 of Anita Mills' "The Rivaux Series" aka "The Fire Series".
No noblewoman in all of Britain was more beautiful -- or more defiant -- than raven-haired, emerald-eyed Elizabeth of Rivaux, daughter of Catherine and Guy. After a disastrous first marriage Elizabeth, left with a secret shame, refuses to accept any man. Now on her way to Harlowe, the border castle that is her birthright, she is kidnapped by Giles of Moray known throughout the border country as "The Butcher". Even her shrewish tongue couldn't stop Giles from pledging his freedom to win her. Unexpected passion envelopes Elizabeth and she is forced to surrender her love to this Scottish lord.