Predator by Ramona Forrest
Martha Lavery Chance is a woman with a dark secret—a wild-hearted, amoral, alter personality, Serena, created to save her sanity as a child in danger. At present, living with a wonderful man, Martha refuses to marry him, believing it will cost him his life. A detective, he brings home the sad tale of another small child taken, sexually devastated, and murdered. His anguish sends her alter, Serena, into a rage against child predators, and she aches to get busy again, destroying the sexual capacity of these monsters. Can she disable a few more of those predators while staying free of prison herself?