What makes the ending of "The Necklace" Ironic? Atleast a one paragraph response!

The necklace is ironic in the fact that when the necklace is borrowed it is believed to be a real diamond necklace. When she loses the "diamond necklace" she works very long to repay the person she borrowed from because she thinks the necklace she lost was worth much money. When she gives the money to the person she borrowed from and confesses that she lost it she was told that the necklace was a fake and that she worried and worked for many years over nothing. This is an example of situational irony. She thought the necklace was worth very much money when it was really only worth very little