Until You (Westmoreland Saga Third book) by Judith McNaught
Sheridan Bromleigh, a school teacher for wealthy young ladies is hired to escort one of her students, heiress Charise Lancaster, to England where she is to meet her fiance. When Charise elopes with a stranger, Sheridan is left perplexed on what she will have to tell Charise’s intended, Lord Burleton.
Standing on the pier, Stephen Westmoreland, the Earl of Lanford, thinks that the young lady coming towards him is Charise and begins narrating to her his unintended role in the fatal accident that involved Lord Burleton the previous night. As she is about to narrate the side of her story.
The next thing that Sheridan knows once she woke up is that she is referred to as Miss Lancaster and that she is regularly falling in love with the handsome earl.