The characterization of Madame Loisel tells us that she is a woman with no expectations. According to the text, she "allowed herself to be married" to a clerk as she, herself, was born to no wealth or name. Because of her social inferiority, she is unable to establish powerful social relations. This also means that she would come into a marriage penniless and entirely dependent. All of this is summarized when it says:
She had no dowry, no expectations, no way of being known, understood, loved, married by any rich and distinguished man...
We could argue that she was a woman who was not in the marriage for love, that lived in a consistent state of disenchantment, and that perhaps, not knowing any better, she is used to the simple life, knowing in her heart that this is all she will ever get.
However, the irony comes in the form of her actual mindset. She does want the better things of life. She is not used to the simple things and she does dream of riches and awesome things coming her way. She wanted to be an aristocrat, a rich woman, or someone very flashy and financially stable. This is a sad, ironic twist considering that she is likely never to experience this kind of life, and yet, she continuously begrudges the fact that she will never live it.
This characterization shows someone who would never be content no matter what. She is already despondent to her husband. She already does not feel appreciative of the little that she does have. She believes that she deserves it all, but does very little to earn it- if anything. Therefore, what we have is a very shallow and selfish woman who only cares for herself, and whose ego is very overblown by a sense of entitlement that she really should not have.