Vanishing Acts by Jodi Picoult

Delia Hopkins has led a charmed life. Raised in rural New Hampshire by her beloved father, she now has a young daughter, a handsome fiancé, and her own search-and-rescue bloodhound, which she uses to find missing persons. But as Delia plans her wedding, she is plagued by flashbacks of a life she can’t recall…until a policeman knocks on her door, revealing a secret about herself that irrevocably changes her life.