The Boy Who Cried Werewolf (2010)

Jordan, a nerdy girl with two left feet, her horror fan brother Hunter, and their dad travel to Transylvania when they learn they've inherited a castle from a mysterious great uncle. The castle holds many secrets and one of them turns the klutzy Jordan into a werewolf. While Hunter finds himself forced to wrangle his newly confident, werewolf sister, he also uncovers a conflict brewing that will pit his family against dark ancient forces.