Tom's Aunt Polly doesn't make anything special in the book until the very end of the novel, but that woman is awesome. Also, we can see her in the previous book Adventures of Tom Sawyer, where Aunt Polly shows us that she's very sharp lady. She's a slow and strict woman with very strong character. Tom doesn’t make fool at all, because of their old deal. And while reading, we see and feel that she loves Tom, while not telling this to him.
Aunt Polly in the Essays