"A Worn Path" by Eudora Welty

I feel that Phoenix is not mentally stable/sane. I wondered if she had alzheimer's throughout the story, which would explain some of her unique behavior/actions. Is her grandson really still alive? Or is she living through memories? I feel that Phoenix is living through the past and just going through an old daily routine. She stumbles her way in to town everyday. Granny is also very "stiff" when receiving money at the end of the story, which I found to be odd. Phoenix is an interesting character throughout this work.