Answer: Marilyn sneaks into a cargo ship that is headed for the Planet of Woden, which is where her brother lives. Her longing to see him is what makes her board the ship. Despite all the warnings that she saw about unauthorized personnel boarding the ship she does so anyway and result in the violation of interstellar regulations. She is then abandoned into space. The reason why they do this is because the Stardust only has enough fuel to reach the destination with the predetermined number of passengers. She is sacrificed so that the others can survive.
