When Mdme. Loisel reads the invitation to the ball that The Minister of Public Instruction and Madame Georges Ramponneau give Monsieur Loisel, she is far from excited, as her husband had hoped:
Instead of being delighted, as her husband had hoped, she threw the invitation on the table crossly, muttering: "What do you wish me to do with that?"
Mdme. Loisel reacts this way because she is the type of woman who, as she is described by the narrator, suffers all the time for feeling that she was "born" to enjoy all the delicacies of life. However, this is not the case at all. Mdme. Loisel is part of a family of clerks, and is also married to one. Her aspirations and wishes do not come from a genuine understanding of how life should be better if you are rich, but from the assumption that money makes everything better.
Therefore, when Mdme. Loisel thows the invitation on the table, she is angry, first, because she does not have a gown to wear to the ball. Additionally, she feels that she should not go because she could never be parallelled to the other women, who surely will be there with new gowns and jewels.
Hence, the best way to describe Madame Loisel's reaction is that she must have thrown that letter with disgust, anger, haughtiness, and with the snob characteristics that are typical of someone who thinks of herself much higher than what she should. For this reason, she feels that nothing is enough: when she goes to her friend Madame Forestier's to borrow jewels for the ball, she picks the shiniest and most noteworthy. The fact that she could not tell right away that the piece that she thought was so expensive was, actually, a fake, is what tells us that Mdme. Loisel only thinks that she was born for bigger and better things. As the narrator tells us, this is way far from the truth:
She dressed plainly because she could not dress well, but she was unhappy as if she had really fallen from a higher station; [...]. Natural ingenuity, instinct for what is elegant, a supple mind are [women's] sole hierarchy, and often make of women of the people the equals of the very greatest ladies.
Hence, her reaction goes from (perhaps) a bit of excitement for the invitation, and then goes to frustration from the realization of not having something nice to wear. It then becomes sadness and anger for not being in a better station in life. Finally, it becomes petulant, for she does not have to be so ungrateful as to slam the envelop across the table after her husband has brought her such nice news.