As much as I enjoy reading Dr. Adams, he misses one crucial point here. The bank teller, while trying to be nice, was inconveniencing a lot of people by indulging the elderly lady.
I've worked with the elderly. They are not usually in any big hurry, but those that live alone are usually desperate for human interaction. The teller could have said, "Why, Mrs Smith, I would love to chat with you, but as you can see, there are many people in line. Why don't you have a seat over here, and we'll talk when I have a free moment?" That would have been respectful to both the elderly lady AND the impatient jerks (sorry Dr. Adams) in line.