Who is Stella Volkova from Pattern Recognition and what is their importance?

Stella is described as a young woman with a soft, pale white face and angular features. She has dark eyes, unfashionably long hair, and speaks with a slight accent. Stella is half of the Volkova twins, who were orphaned when a Claymore mine exploded outside of their home, as she and her family were on their way to a funeral for their grandmother. After her parents were killed in the explosion, her uncle took both girls under his wing and provided them with everything they needed afterward, seeing to the best of care, stimulation and security that his money could buy. Their uncle is a very wealthy man, big in business and importance. Stella and Nora were educated in Paris where she studied business.