In "The Necklace," why was Mathilde unhappy in the early years of her marriage?

Mathilde Loisel is depicted as an unthankful, superficial woman who believes that she deserves
to enjoy a life of luxury. Instead, Mathilde Loisel is married to a lowly clerk who works at the
Ministry of Public Instruction. Mathilde Loisel desperately dreamed of marrying an aristocrat
and suffers from the poverty of her dwelling. She is completely...