To me, the theme of this story is about how adults should deal with children and the emotions that the children have. I believe that the author is trying to say that parents must take their children's emotions seriously.
In the story, Mrs. Dickinson does not really seem to care very much about what Frederick is thinking or what is making him cry. All she really cares about is her image and her vision of what her son should be like.
When Frederick meets the young woman at the duck pond, the young woman acts in a very different way. She seems interested in why he is crying, rather than just telling him to stop. This makes such an impact on him that he does stop crying.
I think the author is saying that Mrs. Dickinson's ways were bad -- that she does not try hard enough to understand her child. Instead, she only thinks about how Frederick's behavior affects her.