Madame Loisel learn how to live humbly as well as the value of hard work. She learns to appreciate what she has instead of coveting things that she does not. I think Mathilde begins to understand that her middle-class life had many blessings.
Madame Loisel came to know the ghastly life of abject poverty. From the very first she played her part heroically. This fearful debt must be paid off. She would pay it. The servant was dismissed. They changed their flat; they took a garret under the roof.
I'm not sure it made her a better person. I think she was more bitter and worn out. She might have understood her folly but she was worse off for it,
Madame Loisel looked old now. She had become like all the other strong, hard, coarse women of poor households. Her hair was badly done, her skirts were awry, her hands were red. She spoke in a shrill voice, and the water slopped all over the floor when she scrubbed it.