Toward the end of the story, Josephine says to Mrs. Mallard that by staying alone in her room, "You will make yourself ill." Why is this an example of irony?

This is an example of a dramatic irony because the readers are aware of something that a character in a literary work does not know. Josephine is very concerned that her sister is suffering from powerful grief, but the reader knows that Mrs. Mallard (Louise) really feels a sense of relief.

Mrs. Mallard actually starts to feel better in her room