What does Marilyn do in her final hour in "The Cold Equation".

When Barton met Marilyn in a ship called EDS, he told her that she should be leaving the craft as her body weights might compromised the mission. He must bring those medical supplies to a planet and with the girl inside the space craft would result them for crash. This situation was understood by Marilyn.

Her final actions in the novel was: she speaks to his brother named Gerry for the last time, she bids him goodbye, reminisced about their childhood and memories. She wrote letters for him and her parents and handed them over to Barton so he could give them her final words with some of her things. When she is ready, she walks to the airlock and steps inside, where Barton closed the door and throw her into space.