Answer:
The act/ behavior of Mrs. Delacroix is ironic for she seemed to have more respect and interest in preserving the tradition than her friend's life.
This instance of irony shows that the villagers hold the power of tradition more important than the barbaric tradition of putting someone to death just for a "good harvest".
Explanation:
Shirley Jackson's short story "The Lottery" set in an unnamed village in an unspecified time/year tells of a village's annual ritual of stoning one person to death as a way of 'offering' for a goof harvest. This ritual is barbaric and the people in the village also knows it but they wouldn't change it anyway.
The present year's lot fell on the Hutchinsons, where another lot drew Tessie out as the year's 'winner'. Mrs. Delacroix seemed to be a close friend of Tessie, for we see them standing together and talking while the lottery was about to start. But once the "winner" had been chosen and Tessie "won", Mrs. Delacroix began to take the biggest stone, "<em>so large she had to pick it up with both hands</em>" and urged Mrs. Dunbar to hurry so that she can get back to her house chores. This is ironic, considering she seemed to be close to Tessie just few minutes back. But now, she doesn't seem to have any remorse or pity for her friend.
The ironic or unexpected behavior of Mrs. Delacroix in wanting to get the "ritual" over with, shows not only her but also the whole village's ingrained practice of the annual ritual. They seem to keep more importance on tradition, even if it seemed barbaric, than saving a friend's life. So accustomed are they to the long standing tradition of the "lottery" that they seemed to know nothing better but observe it and be done with.
