How does Dangarembga make this a powerful and moving moment in the novel?

The author's description of Nyasha's condition is vivid and alarming. She doesn't eat at all unless supervised; she steadily disappears and becomes more animal like in her rebellion against the entrapment she feels. Everyone is frightened for her, and yet, it is her own rebellion and means of rebellion that have over time become responsible for her mental (nervous) breakdown.