disrepair, collapse, dereliction, decrepitude, decay, ruin, shabbiness, destruction

The shabbiness of Mathilde's apartment in "The Necklace" symbolizes her dissatisfaction with her social status and desire for a more luxurious life. It highlights the stark contrast between her dreams of wealth and the reality of her modest living conditions, fueling her sense of resentment and longing for a life of luxury.

To be worn/used.

Example: His clothes were shabby

I despise shabbiness in fashion.

My guess?
Because it represents urban life, despite it's shabbiness.

Mme. Loisel was angry and tortured because she felt that she deserved a better life with luxury and wealth than she currently had. Her dissatisfaction and sense of entitlement led her to resent her circumstances and feel trapped in a life she viewed as beneath her.