This is a great question. In order to appreciate the words "wise guy," you need some context. Let me, therefore, start off with the quote:
"Bite back your tongue," scolded my mother when I cried loudly, yanking her hand toward the store that sold bags of salted plums. At home, she said, "Wise guy, he not go against wind. In Chinese we say, Come from South, blow with wind-poom!-North will follow. Strongest wind cannot be seen."
As we look at the story, Waverly's mother is teaching her what she calls the art of invisible strength. She defines this as a strategy for winning arguments and respect from others. In short, Waverly's mother is trying to impart what she feels are important life lessons. Therefore, to be wise is to learn and use the art of invisible strength.
When Waverly tugs her mom's hand towards a store that sells plums, Waverly's mother scolds her a bit by the words given above in the quotation. In essence she is saying that Waverly should not fight for what she cannot get. To be wise is to know your battles and choose them well.
For the rest of the story, Waverly will grow in this wisdom, and it shows in her ability to play chess. She excels and becomes a prodigy. However at the end of the story, Waverly realizes that her main opponent is her mother.