How does Mathilde's attitude change after she vows to replace Madame Forestier's necklace?

Madame Loisel feels responsible and she vows to replace Madame Forestier's necklace, which costs a fortune. As a consequence, she and her husband work really hard for many years, and she becomes a little more realistic and practical. In fact, instead of wishing to possess garments and jewellery, she dresses and looks like a poor woman, and works as a maid. In fact, she must go shopping herself, as well as bargain and fight for every penny.