What happens to Miss Furnivall at the end of "The Old Nurse's Story"?

At the end of the story, Miss Furnivall yells at the apparition of the father as he tries to hit the woman and child with his crutch. She begs him to spare the child. Then, an apparition of young Miss Furnivall appears and she falls to their feet "stricken down the by palsy" and is brought to bed where she mutters repeatedly, "What is done in youth can never be undone in age" (11).