Big Sister 2000.

Julie Strain is the tyrannical interrogator who commands the dark forces of the future. They abduct Jenny, an innocent woman and enslave her inside an invincible steel fortress. Forced to endure mind-shattering torments, she befriends the other female prisoners who commit unspeakable acts in order to survive. Guided by a mysterious spirit of a woman known only as Big Sister, the prisoners find their inner strengths and over come the insurmountable odds.