Where in the story could Madame Loisel have changed the outcome?

After the fancy party, where Madame Loisel wore the "diamond" necklace she borrowed from Madame Forestier, she returns home and realizes that the necklace is no longer around her neck. Rather than accept her husband's inheritance of eighteen thousand francs and allow him to enter into "ruinous agreements" that would bind him to moneylenders for the rest of his life, Madame Loisel could have returned to her friend and told her the truth: that she had lost the necklace. If she had been honest, it is likely that Madame Forestier would have told her that the diamonds were fake and that the necklace was actually worth a pittance compared to what a necklace composed of real diamonds would be.
Or, going back even further, Madame Loisel could simply have taken her husband's advice to wear flowers instead of jewels. Had she been content to wear two or three beautiful roses, as her husband suggested, she never would have borrowed the necklace to begin with.