Hello Mary Lou: Prom Night II is a 1987 Canadian supernatural slasher film directed by Bruce Pittman, and starring Michael Ironside, Wendy Lyon, Louis Ferreira, and Lisa Schrage. It follows a high school student who becomes possessed by Mary Lou Maloney, a student who died at her high school prom in 1957. The second installment in the Prom Night saga, it was originally intended to be a standalone film, but was retitled and underwent reshoots to capitalize on the success of the original Prom Night. The character of Mary Lou Maloney would also appear in 1989's Prom Night III: The Last Kiss.
(Summary from Wikipedia)