The Welshman's Bride by Blair Bancroft

Although it seems likely she is being married for the magnificence of her dowry, Jocelyn Hawley accepts an offer of marriage from a Welshman. And quickly discovers she is as unprepared for marriage as she is for her new family—a mother-in-law who insists on living in Wales' Medieval past and a sister-in-law who seems to be trying to get rid of her. Jocelyn is also plagued by the problem of her husband's mistress and a series of disastrous incidents—some potentially lethal—that dog her footsteps. As she grows more alienated from her husband, who barks at her to "grow up," she finds herself the classic stranger in a strange land. Where it appears someone is trying to kill her.
Author's Note: The Welshman's Bride is a Gothic novel in the tradition of Victoria Holt, Mary Stewart, Phyllis Whitney, and my previous Regency Gothics, Brides of Falconfell, The Mists of Moorhead Manor, and The Demons of Fenley Marsh. As has happened before, I've created a heroine who has flaws, this one more than most. I hope you'll like her anyway.