Who is Riva Minska from The Cage and what is their importance?

Riva was a thirteen-year-old Jewish girl when her mother, fearing the advance of Germans against the Jews, sent Riva's three older siblings out of the country. Riva and her three younger siblings were kept in Germany because of her mother's expectations that the Germans would not harm women and children. Riva was soon caught up in the hatred against the Jews, forced to wear a yellow star to signify that she was a Jew, and was subjected to hatred and ridicule.