She didn't do anything wrong. She "won" the lottery by getting her ticket drawn on the lottery day. The story is ironic on many different levels one of them being the fact that Mrs. Hutchinson won the lottery but wins death instead of something great like a million bucks. Her only fault throughout the story was getting to the reading of the numbers a little late, perhaps showing a little callousness on her part but that isn't what gets her killed. The village's tradition (as many cultures have done) of sacrificing someone each year on June 21st (note that this is the day of the summer equinox) is what killed her.
In this short story Mrs. Hutchinson was stoned to death by the villagers as a custom of sacrifice. Every year the whole village got together, reached in a black box and drew out a piece of paper. If the paper had a black mark on it that person would be sacrificed for the "good of the village."
Mrs. Hutchinson didn't do anything wrong, she was just unlucky enough to draw the paper with the black mark.