Who is Ruth from Never Let Me Go and what is their importance?

Ruth is the third of the three main characters, and the first of them to die after making organ donations. She is a popular girl at Hailsham, organizing clubs and groups of girls that center around herself. She is also quite jealous, she reveals as an adult, manipulating Kathy and Tommy in order to keep them apart. Her behavior eventually contributes to Kathy's decision to leave her friends and become a carer.