How is the character of Ruth significant to Never Let Me Go as a whole?

Each of
the clones must confront their own future in their own way, and much depends on their
personality, which is that of the original from whom they were cloned. As children, they are not
fully aware of the gravity of the situation. The Hailsham students, who largely live in their
own world, can invest in the kinds of games and fantasies that children tend to take
seriously.

Ruth does so more extensively than the others. Her initial
interactions with Kathy show that she has a domineering personality but also suffers from
extreme anxiety; these complementary features are made apparent by the extensive rules she
imposes, her insistence on being right, and her excessive pride in allegedly being an adults
favorite. While Kathy cannot fully understand why Ruth insists on taking charge, she goes along
with her whims.

Similarly, as Kathy and Tommy grow closer, Ruth must
intervene and make Tommy her boyfriendbut ultimately her...