The Bones of the Holy — Jennifer Allison

When Gilda Joyce's mother announces her engagement to a man from St. Augustine, Florida, Gilda is appalled. She hasn't even given him the "Joyce Family Application" yet! But as the wedding preparations get under way, Gilda realizes she has much bigger concerns. Why does her soon-to-be stepdad keep calling Mrs. Joyce by his ex-wife's name? And why is Mrs. Joyce acting like she's possessed?

With only a few short days before her mother says "I do," Gilda knows this much for sure: it's going to take every ounce of her sleuthing skill and psychic savvy to solve this one!