Well, it could be centered around exploitation. The 'ninny' might be constantly taken advantage of, and through this, the theme could be highlighting the power dynamics and unfairness in certain relationships. For example, in a work or social context where the 'ninny' is made to do things without fully understanding the implications.
Perhaps the main theme is self - discovery. The 'ninny' starts off in a state of ignorance or simplicity. As the story progresses, they might start to learn more about themselves, their worth, and how they should be treated. This could be shown through various interactions and events in the short story.