What is going on with the narration? Often it seems completely objective: "They formed a congenial group sitting there that summer afternoon." Other times it focuses in on Edna’s thoughts: "Mrs. Pontellier was beginning to realize her position in the universe as a human being, and to recognize her relations as an individual to the world within and about her." (There’s no way a narrator pretending to be a fly on the wall would know that.) What takes this text from third person limited to third person omniscient, however, are the scenes where Edna is not present.
Let’s take a closer look at the scenes lacking Edna: the opening scene with Mr. Pontellier (and the parrot), the scene where Adele warns Robert to stay away from Edna, the scene where Mr. Pontellier seeks medical advice, and the last chapter with Victor and Mariequita’s points of view. The non-Edna scenes show us the ways in which Edna is discussed/viewed by those close to her. This third person omniscient business, in other words, helps us understand Edna. In the opening pages of the novel, Mr. Pontellier views Edna as his property. During Adele’s conversation with Robert, we see that Adele views Edna as a traditional woman who will take flirtation seriously. The last two non-Edna scenes, however, show us that Edna’s behavior has become incomprehensible to those around her. Mr. Pontellier is convinced she’s mentally unbalanced, and Victor and Mariequita are confused by her sudden appearance at Grand Isle and subsequent insistence on going for a swim.