How does Madame Loisel go about getting something special to wear to the party in the story "The Necklace"?

In "The Necklace," Mathilde Loisel goes to her friend, Mrs. Forrestier, to borrow the necklace for the ball.  Mathilde had told her husband that she had no fine jewelry or a dress to wear to the party, so her husband gave her money to purchase a dress (he had saved up money to buy himself something).  He also suggested that she go see Mrs. Forrestier to borrow some jewelry for the evening.  Mrs. Forrestier agreed; however, she did not tell Mathilde that it was a fake diamond necklace. Mathilde lost it at the ball, as we know, and then she and her husband had to work for 10 years to pay off the necklace.  In the end, Mathilde finds out the necklace was fake to begin with and that is how the story ends.