Why does Mariela, who bullies her classmates, remain a sympathetic figure in the story, Siberian Tiger Park?

In Siberian Tiger Park, Mariela, unlike the other girls, reads Anne Frank: The Diary of a Young Girl. Because she reads a book about a girl imprisoned, who eventually dies, Pachico implies that Mariela, too, is somehow imprisoned and fated to an untimely death. In M+M, Martin has already implied that Mariela has died (although he imagines that she hasn’t), rendering her a sympathetic figure in Siberian Tiger Park, even though she acts as a kind of bully to the young girls.