The Sitter (1991)

In this exciting thriller, schizophrenic Nell throws her mother down the stairs, then heads off to a babysitting job. Nell is completely delusional and thinks that the girl she is babysitting is her daughter. She causes a lot of trouble, including killing a dog and murdering her stepfather and a maid whom she thought would tell on her. Can she be stopped before she harms her babysitting charge?