Who is Zahra's Sister from Year of the Elephant: A Moroccan Woman's Journey Toward Independence, and Other Stories and what is their importance?

Zahra's sister was described as a beautiful woman. Her beauty caused her to be haughty and vain. Zahra's sister confronted Zahra about her divorce and insisted that she and her husband take care of Zahra. But Zahra refused her sister, remaining fiercely independent.