Jewels by Danielle Steel

On Sarah Whitfield's seventy-fifth birthday, memories take her back to New York  in the 1930s. To a marriage that ends after a year, leaving Sarah  shattered. A trip to Europe with her parents does little to  raise her spirits, until she meets William, Duke of Whitfield.  In time, despite her qualms, William insists on giving up his distant right to the British  throne to make Sarah his dutchess and his wife.