Why doesn't Madame Loisel enjoy her life at the beginning of the story?

Madame Loisel is the picture of discontent at the opening of the story.  She has a modest life married to a man who makes a modest income, but she spends her time wishing away the life she has for something more.  She wishes to be rich, to be envied, and to be desired.  She is jealous of those friends who have surpassed her on the social ladder, and she even refuses to visit them because she is ashamed of her station.  She feels intimidated by the success of her good friend Madame Forestier, and she envies her apparent life of leisure.  She is so absorbed in what others have that she fails to appreciate the life she does have.  She is obviously not of the lowest social class, because Maupassant tells us she has a young girl who does her housework for her.  Because of this discontented spirit, nothing her poor husband does for her ever seems to be enough.  This attitude is what eventually causes her downfall.