A Girl, a Ghost, and the Hollywood Hills — Lizabeth Zindel

When Holly's mother dies unexpectedly, she thinks things can't get much worse. But then her dad starts dating again. And his new girlfriend is Holly's aunt -- her mom's sister! Aunt Claudia is known in Hollywood as the Queen of B Movies. Horror films, zombie flicks, she's made them all. Holly never liked her aunt, but now she positively can't stand her. Especially once the ghost of her mother appears and tells Holly that Claudia was to blame for her death.
Inspired by Hamlet, this funny novel about the danger of family secrets is a modern comic take on a classic Shakespearean tragedy.