Shadows of Desire by J. H. Gagnepain

Time Travel, Historical Romance Tiaret Burdock is a young, millionaire who has had her fair share of unfortunate events. When lifes responsibilities become too much for her to handle she spirals into a state of uncertainty and self-pity, which crashes her straight into a lake. Frightened and confused she awakens in the year 1415! Tiaret soon meets up with quick-witted knight, Sir Brice Ashford, who reluctantly agrees to escort her to Castle la Gloxina and possibly awaiting answers. Together they must survive a forest riddled with thieves, quicksand, and a quickly growing attraction for one another. Time and circumstances make their relationship forbidden, but not even six-hundred years can stop the magic between them. A magic that draws an evil force, neither of them sees coming, as they are swept away into Shadows of Desire.