Who is the class bully in Gina's fifth-year class in the novel, Abigail?

Mari Kis is Gina’s archenemy in the fifth-year class, who becomes one of her closest friends at the Matula. Fearless and intelligent, Mari Kis shoulders the blame and lies to prevent the entire fifth-year class from being punished when Gina betrays to Gedeon Torma the secret of the class wedding to the inventory items. She leads the class in their bullying of Gina and escalates their attacks after Gina accuses her of theft.