In "The Story of an Hour," why does Chopin describe Mrs. Mallard as "a child who has cried itself to sleep continues to sob in its dreams"?

When Chopin introduces Mrs. Mallard in the story, the protagonist is overwrought with emotion upon hearing of her husband's death.  She sobs uncontrollably in her sister's arms and then retreats to her room.  As she stares out the window at the gorgeous spring day, she,

"[sits] with her head thrown back upon the cushion of the chair, quite motionless, except when a sob [comes] up into her throat and [shakes] her . . ."

Most readers have witnessed a child who has thrown a temper tantrum or who has gone to sleep after tiring itself from sobbing.  This is the image Chopin creates.  At this point in the story, the reader would most likely interpret the image as a portrayal of Mrs. Mallard's extreme grief.  She is so spent with emotion, that she cannot move from the chair or think of anything else.  It seems that she, like many humans, suspends reality in the hopes that she will wake up to find that reality was only a nightmare.

However, Chopin's surprise ending should encourage readers to rethink this scene.  When Mrs. Mallard hears of her husband's death and illustrates the normal reaction to the death of a loved one, she then begins to think of how her life will be different in a good way.  She is as a child who is about to begin life anew, and instead of waking up and still being in a nightmare, she "wakes" up to reality and begins to realize all the positives that await her.