Strike of the Tortured Angels (1974)

Julia, aged 18, kills her sister by pushing her from the 12th floor; and at the discotheque, she hits her classmate's head with a beer bottle. Julia is arrested and sent to the Girls Rehabilitation Centre where she is tortured and savaged by the guards. The film was originally a Korean movie from 1974 titled "Julie, a Half-blood" (https://www.kmdb.or.kr/eng/db/kor/detail/movie/K/02793), released 10 years later as a HK movie with fake credits.

Action! Betrayal! Hatred! Bloodshed! Girls! Girls! Girls! Beware of the Nightmare