The stepsister / Stine, R. L

Emily finds it is impossible to like her new stepsister. Before long Emily is living in total fear of her. Then Emily learns that her stepsister wrote in her diary that she murdered someone!.

Emily has a new stepsister, who takes over everything and may be a murderer.

Emily's discovery that her lying, stealing stepsister may also be a murderer places her own life in danger.

Emily finds it is impossible to like her new stepsister. Before long Emily is living in total fear of her. Then Emily learns that her stepsister wrote in her diary that she murdered someone!.