What does the character want? The girl wants to see her brother.
Is the character likely to succeed? Not likely. If she is caught, she will be in some sort of trouble for stowing away on a ship without permission. And even if she's not caught she does not know the specfic details of her brother's whereabouts.
Is the character a good person? Yes. She is a sweet and innocent young lady; however, she is too ambigious with her plan.
What does the story mean? The story follows a young girl wanting to see her brother. Therefore stows away on a ship that has already reached its maximum weight. As a result, the captain, kindly explains she has to be ejected into space before they all lose their lives.
What is the main idea of the story? The consequences of the choices you make are unavoidable.