Heart of the Diamond by Carrie Brock

Blake Dylan, The Earl of Diamond, has a heart of ice. The time has come for him to return to England and enact his plan of vengeance, even if it means wedding the daughter of his sworn enemy. Lady Nicole Langley has vowed she will not marry unless for true love. When she is lured into a compromising situation with a handsome stranger her worst nightmare begins. Now, to save them both, Nicki must wage a campaign to win the heart of the Diamond.