Mona is Lolita's BFF at the Beardsley School for girls. She is way too loyal for Humbert's liking because she won't out Lolita for her bad behavior. Humbert burns to know what secrets Mona holds. Humbert describes Mona as an "elegant, cold, lascivious, experienced young female" (2.9.1). At one point, she clearly develops a crush on Humbert; he's not interested.