Miss Redmond's Deception by Sandra Cox
Blurb: When Captain Richard Greyston encounters three figures in a graveyard, he takes them for a spectral visitation until he realizes it is two young ladies—in their nightgowns, no less—and their spinsterish companion. A spinster with slender limbs and an enchantingly velvety voice.
Pembra doesn’t care a whit for the captain’s opinion of her, even after circumstances force them into a sham betrothal. But when a gypsy warns her that his life hangs in the balance, she begins to realize that her heart is not so uninvolved as she might like to pretend.