The correct response is:
It shows her hard work was for nothing.
In "The Necklace," situational irony occurs when Mathilde Loisel's desire for a life of luxury leads her to borrow a necklace, only to lose it and spend years in poverty to replace it, only to find out in the end that the original necklace was a fake. This irony emphasizes the futility of her sacrifices and the harshness of her situation, adding deeper meaning to the theme of wealth and superficiality.