Earthbound by Artemis Greenleaf

"I didn't believe in ghosts, not until I became one."Schuyler Ramsey just wants to be like the other kids in school. Too bad she's dead. She haunts a farm in windswept western Ireland, along with some of its previous inhabitants. When she partially materializes in front of her sister at breakfast, she is propelled on a quest to stop a fake TV psychic from visiting the farm and stirring up trouble. Along the way, she visits a famous pirate, helps a mermaid rescue a basking shark from fishermen, and encounters Nicniven, queen of the dark elphs. But Schuyler soon finds that the Haunted Planet television show is the least of her problems. As her world unravels, can she find the strength to save her sister from a monstrous evil?