Blind Faith by Ellen Wittlinger

After Liz's grandmother's sudden death, her mother spirals into a severe depression and becomes fascinated with a church whose ministers claim to communicate with the dead. Liz's father, an atheist, disapproves causing an increase in the tension in her home. At the same time, Liz is also dealing with the sudden arrival of her cranky neighbor's daughter Lily, and children Nathan and Courtney. Nathan and Liz hit it off right away, but Nathan has problems of his own to deal with, including his mother's terminal cancer. A very emotional story with strong and rich characters that are likeable and easy to connect with.