In Chapter 21 of "Jane Eyre", why does Mrs Reed still talk about her son as if he were still alive?Why does she talk about him as though he is...

Mrs. Reed has always been somewhat delusional where her son John is concerned.  Her coddling of him when he was young and the complete blindness with which she accepted his utterly selfish nature evidenced an unnatural capacity for self-deception.  The stress of John's demands on the family finances over the years and the shock of his suicide cause his mother to suffer a stroke, and when Jane meets with her, Mrs. Reed is not completely lucid; her "wandering look and changed utterance told what a wreck had taken place in her once vigorous frame".

When Mrs. Reed talks to Jane now, not only does she speak of John as if the "poor boy" is still alive, but she also speaks to Jane in the third person, talking about Jane as "that child".  Her long-cultivated blindness towards the truth where John is concerned is now exacerbated by an inability to distinguish present reality from memory because of the delirium caused by her illness.  Another contributing factor might be that it is just too difficult for Mrs. Reed to accept the horror of John's death and the monstrosity of her behavior towards Jane.  It is easier for her to deny to herself that her son is gone, and to never acknowledge Jane's current presence when speaking about the past, distancing herself even further from reality (Chapter 21).