The art of deception - Nora Roberts

Adam Haines was an artist visiting the Fairchild mansion to do some undercover digging, and that was a problem for a man who preferred to be straightforward. An even bigger problem was Kirby Fairchild, daughter of the world-famous painter he'd been sent to investigate. She was part child, part elf, and the most fascinating woman he'd ever encountered.
However, Kirby had a disconcertingly fluid sense of right and wrong -- one completely at odds with Adam's own code of ethics. Adam wished he wasn't wrapped quite so tightly around her little finger