Who is Nyasha from Nervous Conditions and what is their importance?

Nyasha is Tambu's cousin and the daughter of Tambu's uncle, Babamukuru. Nyasha spends five years in England during her formative years and the return to Africa is a culture shock from which the girl never entirely recovers. She and Tambu are great friends as children but have grown far apart by the time of her return to Africa. When Tambu goes to live with Nyasha, there is not an instant connection, but it's not in Nyasha's nature to ignore another young girl in the household; though it takes some time, they become friends again.