The Delacroix family is in the mix right from the start. There's Dickie Delacroix, who gathers his stones with the other boys, there's Mr. Delacroix drawing his strip of paper, there's Mrs. Delacroix, chatting happily with Mrs. Graves and Mrs. Tess Hutchinson—and then there's Mrs. Delacroix picking up a stone so large she needs to use both hands to pick it up.
Let's start with the name, Delacroix.
Critic Helen Nebeker has pointed out that "Delacroix" means "of-the-cross" in French. Nebeker draws particular attention to Jackson's elaboration that the villagers pronounce "Delacroix" (de-la-KWAH) as "Dellacroy." In other words, argues Nebeker, the villagers are perverting the cross, the big Christian symbol of martyrdom: far from being a willing sacrifice, the lottery makes an absolutely unwilling, hypocritical woman bear the burden of the community's ritual murder (Source).
We find it striking that Mrs. Delacroix is the only person who speaks to the otherwise silent Mrs. Graves, wife of the even more silent postmaster. In retrospect, Mrs. Delacroix's friendly relationship with the Graves family foreshadows her willingness to kill Tess Hutchinson with a smile on her face. The lottery appears completely natural to her, so much so that it doesn't strike her as a contradiction to chat happily with Tess one minute and attack her the next.
Mrs. Delacroix's reversal is perhaps the most obvious example of the deadening effect that this tradition has had on the hearts and minds of the villagers; she seems so unconscious of her own inconsistency that it would be difficult to call her betrayal of Tess "hypocrisy."
It's not conscious enough to be hypocrisy—Mrs. Delacroix really seems incapable of seeing how vicious and inconsistent she is being. And that's possibly the most horrible thing about the ending of this story: none of them know what evil they are doing.