Soul Mate by Catherine Bybee

Kari Pearce lives the life of a lone werewolf. No one knows of her affliction, not even her sister. When she hears of a missing child up in the Sequoias, Kari goes on the hunt to find the child and her abductor before tragedy can occur. Saving the child is easy; avoiding the FBI agent associated with the case is not.
Agent Nick Murdock knows he’s seen Kari before, but damn if he can remember where. There’s one thing he knows for sure. Kari Pearce, with her blond hair and piercing blue eyes, is hiding something. And Nick is going to find out what.