Kate Chopin wrote during the Realist period. Therefore, her texts were meant to depict life as it was. Characteristically, these authors wished to depict life as it was; without justification and interpretation. The Realist focused upon the character over the plot, events are plausible, tone and diction reveal common language and understanding, and the author is objective.
Therefore, based upon these characteristics, one would be hard pressed to state that the narrator, or Chopin, endorses anything which Mrs. Mallard does. The story is told as it is happening and the author (narrator) is simply detailing the action for the reader. Texts of the Realistic movement were written in a play-by-play manner. The narrator (a detached, third-person limited narrator) does not interject personal thought and maintains distance from the characters and the story so as to do so.
On the other hand, one could justify just about anything based upon personal interpretation and justification. A reader would simply need to pull pieces from the text which support their feelings about the speaker's endorsement or feelings about Mrs. Mallard. This would be based solely upon your own understanding and justifications made regarding the character of Mrs. Mallard and how you feel about the narrator's feelings about her.