Orbiter 9

The plot follows Helena, who has lived her whole life on what she believes to be a space ship. She is isolated and alone, her parents having told her they would commit suicide so that she could survive, due to an urgent depletion of oxygen aboard the ship. When an engineer named Alex boards her ship for repairs, she invites him to have dinner with her. Following this, she approaches him in his cabin where he is asleep, and says that she has never been kissed. They make love. Read more on Wikipedia.