I first read this story in 10th grade, and the entire situation continues to haunt me - it is one of those fabulous stories that will never leave you.
I've thought about it this way: Losing the necklace made her work harder and sacrifice more than she ever had before. Consider how much (money) she and her husband made to replace it.
Hypothetically, had she not lost the necklance but if they could work that hard to make as much money, perhaps that short time of sacrifice could have been a small nest egg they could have built up to eventually have a slightly higher quality of life. Or, what if she had just been honest (after she made enough money) and then got to keep most of it... I think in that case the work might have seemed worth it.
But then you have to realize, that had the necklace never been lost, the work put into replacing it never would have happened. In fact, her life probably wouldn't have changed at all, except that she would still be living in bitter envy of those who had more than she did. Without some sort of calamity to spark her into action, I doubt Loisel would have been capable of making a major life change on her own.
In my opinion, Madame Loisel's life would have been much easier if she had not lost the necklace, but it would still not have been any more satisfying to her. I say this because she was not happy before she lost the necklace and there is no reason to believe that she would have gotten happier.
Mme Loisel was unhappy because she felt she deserved a richer and more elegant lifestyle than she and her husband could afford. When she lost the necklace, their lifestyle got much worse. They had to work much harder and have even fewer luxuries so they could buy the replacement necklace. But if she had not lost the necklace, their life would have continued just as it had. They still would not have had enough money for her to live in the way she wanted. Therefore, she would not have been any happier.
This shows that her life was really made quite miserable by her inability to accept her circumstances.