Spirit World by Krystalyn Drown

Riesa Adair can hear the dead, but somewhere between her summer in a mental institution and her stepfather's attempt at an exorcism, she learned to keep quiet about it. But that doesn't mean the voices have gone away. A powerful Spirit has taken notice of her, and he plans to use her unique talents to gain control of the human world. Even worse, there is a prophecy that says he will succeed.