Ginger Snaps 2: Unleashed (2004)

Brigitte has escaped the confines of Bailey Downs but she's not alone. Another werewolf is tailing her closely and her sister's specter haunts her. An overdose of Monkshood - the poison that is keeping her transformation at bay - leads to her being incarcerated in a rehabilitation clinic for drug addicts where her only friend is an eccentric young girl by the name of Ghost.