Minna and the Dreambuilders Kim Hagen Jensen

Minna’s life is turned upside down when her dad’s new fiancée, Helena, and her daughter Jenny move in. Her new stepsister, Jenny, turns out to be a mean terror and Minna is frustrated. She wants her gone! One night Minna discovers a world behind her dreams,
where dreambuilders create our dreams. Minna discovers that she can manipulate Jenny's dreams. But interfering with the dreams has dire consequences, and Minna goes too far, so Jenny ends up in a coma. Everyone says it’s an accident, but Minna knows it’s her fault. Minna must enter the dream world one final time to face the living nightmare she has created, in order to save Jenny and her new family. Minna learns that the only way to make her dreams come true is to wake up.