In "The Jewelry," what sentence hints at the wife's infidelity?

The following sentence hints at Monsieur Lantin's wife's infidelity.

His income, which, in the hands of his wife, covered all household expenses, was now no longer sufficient for his own immediate wants; and he wondered how she could have managed to buy such excellent wine and the rare delicacies which he could no longer procure with his modest resources.

Monsieur Lantin has an annual income of three thousand five hundred francsfrom his job as chief...

The following sentence hints at Monsieur Lantin's wife's infidelity.

His income, which, in the hands of his wife, covered all household expenses, was now no longer sufficient for his own immediate wants; and he wondered how she could have managed to buy such excellent wine and the rare delicacies which he could no longer procure with his modest resources.

Monsieur Lantin has an annual income of three thousand five hundred francsfrom his job as chief clerk in the Department of the Interior. Yet his wife is able to provide "excellent wine and ... rare delicacies," and when she dies she leaves behind a collection of jewelry which is worth about two hundred thousand francs. 

The author does not answer the obvious question of whether Madame Loisel had one lover or more than one. She seems to have been receiving money as well as jewelry, because she was spending much more than her husband was earning, and yet she was not apparently selling any of her jewelry. It would seem that she must have had more than one lover. She probably had one rich man who gave her the jewelry and one or more others who could not afford to buy such expensive presents but who gave her money.

Maupassant mentions Monsieur Lantin's employment several times. The author even includes a scene in which Lantin goes to resign.

Suddenly he thought of his employer. He drove up to the bureau, and entered gaily, saying:

“Sir, I have come to resign my position. I have just inherited three hundred thousand francs.”

This little scene plus the previous references to Lantin's job at the Department of the Interior are intended to show the reader how it would have been quite easy for Madame Lantin to cheat on her husband. He would have been gone all day for six days a week. She didn't have any children and would have been free to meet her lover or lovers for several hours. One might wonder whether she ever invited them to her home--but that would be living dangerously!