Grave Surprise by Charlaine Harris

With an invitation from a skeptical college professor, Harper Connelly finds herself in a graveyard seeking out the cause of death of the cemetery's long buried occupants. To her surprise (and the surprise of everyone else present) Harper finds two bodies in one grave, one of which is the body of a recently missing young girl. Now, with all eyes on her, Harper and her partner Tolliver must find the young girl's killer and solve the mystery of her death before she's forced to take the blame.