How is the protagonist/narrator transformed?

Unfortunately, she is transformed from a normal woman into a mentally ill woman. The narrator is not crazy when her husband decides on the "rest cure" and locks her up in the room with the yellow wallpaper. She is understandably grieving after her miscarriage. Her melancholy is expected after such a traumatic event. It is not until her husband lock’s her up that she descends into mental illness. She is locked alone with no way of expressing herself. She ultimately becomes mentally unbalanced having no respite from this torture.