The Boatman's Daughter by Andy Davidson

Ever since her father was killed when she was just a child, Miranda Crabtree has kept her head down and her eyes up, ferrying contraband for a mad preacher and his declining band of followers to make ends meet and to protect an old witch and a secret child from harm.

But dark forces are at work in the bayou, And when the preacher makes an unthinkable demand, it sets Miranda on a desperate, dangerous path, forcing her to consider what she is willing to sacrifice to keep her loved ones safe.