Sister (2014)

When unstable Connie is tragically widowed, she finds it impossible to care for her delinquent adolescent daughter, Niki, forcing her son, Bill, to take his sister in. As the two begin to forge a healthy bond, well-meaning Bill implements his own method of treatment for Niki’s mental troubles, but, when turmoil persists, he must reconcile his beliefs with what actually may be best for his sister.

Source: TMDb