Confessions of a Murder Suspect by James Patterson and Maxine Paetro
 372 pages.

Tandy is the last of the Angel children to see her parents alive. She is doesn't know how they were killed or by whom. As she goes about trying to figure out who is responsible, she questions her role, if indeed she was involved, and the role of her brothers and uncle.  The police are very keen on it being one the children. In her search for answers she finds that what is outwardly displayed isn't always what is truly going on.
Little Miss Curious