The transformation that occurs in Mrs. Mallard is chronicled by the character's nomenclature. For, in the beginning of the narrative, she is called Mrs. Mallard and the impersonal "she," which denotes the subservient role that she plays as the wife of Bently Mallard under the femme covert laws of her Victorian era. So repressed is she that the news of her husband's death
pressed [her] down by a physical exhaustion that haunted her body and seemed to reach into her soul.
She climbs the stairs, goes into her room, and sits with her head thrown back upon the chair, motionless. Slowly, the feeling of freedom enters her consciousness.
She was beginning to recognize this thing that was approaching to possess her, and she was striving to beat it back with her will....
Finally, she abandons herself and utters under her
"free, free, fee!"... "Free! Body and soul free!" she kept whispering.
It is at this point that "she" becomes specifically "Louise" as her sister calls out her name, begging her to open the door and asking, "What are you doing, Louise?" Now an individual with her own separate identity, "Her fancy was running riot along those days ahead of her" and there is a "feverish triumph "in her eyes as she stands at the top of the stairs "like a goddess of Victory." However, Bently Mallard enters through the front door and Louise returns to a mere "she" as she dies of heart disease--a "joy that kills" her individual identity.
The massive change that occurs in the character of Mrs. Mallard of course is due to firstly the news that her husband has died and secondly that he has not actually died. The first bit of news triggers initial grief, which quickly subsides into feelings of liberation and freedom. The news of the death of her husband makes her realise just how oppressive marriage has been to her:
There would be no one to live for her during those coming years; she would live for herself. There would be no powerful will bending hers in that blind persistence with which men and women they have a right to impose a private will upon a fellow creature.
For Mrs. Mallard, the death of her husband means being "free," as she repeats to herself, and it means being able to open herself to the years ahead that would "belong to her absolutely." However, having experienced and savoured such a tantalising taste of freedom and having undergone this epiphany, she has it seized back from her abruptly and shockingly. This is why she dies at the end of the story. When she sees her husband very much alive, and is forced to acknowledge that the freedom she has just so deliciously savoured has been snatched back from her, her heart cannot take the shock, and she dies. The final sentence of the story is an excellent example of irony: she dies of "joy that kills," though it is only the reader that knows it is the joy of the freedom she experiences in widowhood that kills her when she recognises she will have to relinquish it, not the joy of seeing her husband alive again, which everybody else assumes is the reason for her demise.