Even after her husband makes a sacrifice and get her a dress, Mathilde wants more.

She wants fine jewelry to match her new dress, so she visits her friend Madame Forestier and borrows a lovely diamond necklace which she assumes is real (though if she had been less self-absorbed she might could have figured out it was a fake). She attends the ball with such excessive pride that she ditches her husband and does exactly what she pleases because this is her night, the night she finally deserves.

That necklace is the symbol of her excessive pride, and it gets worse right after she loses it. Mathilde is much too proud to tell her friend that she lost the necklace, so she and her husband are forced to borrow outrageously in order to replace it. For the next ten years, the two of them work hard, really hard, to pay back what turned out to be unnecessary loans. During this time the Loisels really do live as she had always felt they were living; it is mean and unpleasant, but Mathilde learns a few valuable things.

In that decade of work and sacrifice. Mathilde learned how to be content with much less. Her appearance has changed, as well, and Madame Forestier barely recognizes her when the two women meet one day. Mathilde finally shares the truth that the necklace she returned was a replacement, but she and her husband have finally paid off the debt. Of course the great irony is then revealed: the original necklace was not real.

By the end of the novel, it is clear that Mathilde has come to appreciate the value of hard work and sacrifice, so the necklace at the end of the story is symbolic of a different kind of pride--pride in herself and her husband for working hard, pride in finishing a task and accomplishing a goal, even pride in what she and her husband have, something she would never have felt before losing the necklace.

From excessive, arrogant pride to the pride of accomplishment in a job well done, the necklace remains a symbol of pride in this story. 

It is telling that Mathilde Loisel "had no dresses, no jewels, nothing. And she loved nothing but that [...]." Though she loves jewels, she does not have the skill or the knowledge to tell real jewels from fake ones, just as she lacks the ability to discern what is truly important in life from what only seems important. This could be seen as a clue which foreshadows the necklace's value (or lack thereof). In addition, Mathilde is incredibly concerned about appearances rather than realities. She believes that she "shall look like distress," and declares that she would almost rather just stay at home if she has no jewels to wear to the fancy party. She believes that "there's nothing more humiliating than to look poor among other women who are rich." Again, to her, everything is about looks and not about actual value. The very flaws in Mathilde Loisel's own character would seem to foreshadow her inability to choose a piece of jewelry with real value, as she does not properly value her husband, his love, or his desire to make her happy. Next, when she does choose the necklace from her friend, Madame Forestier's collection, the narrator tells us that she "fled with her treasure." The use of the word her rather than the word the seems significant here: a truly valuable necklace would be a treasure to anyone, but without the ability to tell what looks real from what is real, Mathilde only thinks she has a treasure. The necklace looks real, and so she cannot tell the difference.

Guy de Maupassant details the youth and early married life of Loisel in the short story “The Necklace.” These details become significant when it is revealed that the necklace was a fake.

Loisel, a beautiful girl, came from a poor background. She had no material goods when she marries a working class man, but she has a penchant for the finer things in life. The author tells the reader she longs for fine clothes, food, and jewels to the point of making herself miserable. She longs to be something she is not.

When her husband procures a much coveted invitation to a dance, her reaction is troubling to him. She claims she needs a new dress and jewels, which she knows they cannot afford. Her husband gives her his savings to purchase a dress but cannot buy jewelry. He suggests she wear flowers or borrow something from her school friend who is rich and has many pieces of jewelry for her to choose from.

All of these details take on more significance when it is revealed the necklace was a fake.

Since Loisel was never exposed to finery, she had no way to know the necklace she chose was not real. She did not realize her friend, Madame Forestier, agreed to lend her the necklace without hesitation or reservation even though the two rarely saw each other since their school days.  If the necklace was real diamonds, one would expect the friend to be less willing to part with it so easily.

Madame Forestier went to her dressing-table, took up a large box, brought it to Madame Loisel, opened it, and said: "Choose, my dear."

It seems Madame Forestier thought she was aware of the fakery but obviously she was unaware of Madame Loisel’s naivety. The irony of the husband giving up his savings for his wife’s dress is exposed because both of them end in a life of drudgery for a fake piece of jewelry. If she did not put on airs by trying to be something she was not, and told her friend the truth about the necklace, their lives could have been very different.