Marilyn in 'The Cold Equation' is a GOOD person.
Marilyn is an innocent but ignorant eighteen years old girl who had not seeing her brother for ten years. She believed hiding in the Stardust ship, which is going to the place where here brother lives is a good mean of seeing her brother again. She had good thoughts and good intention but was not aware of how her presence in the ship will negatively affect and jeopardize the lives of others on aboard the ship.