Jealousy. It's different from covetousness. One covets something already possessed by someone else--fame and fortune, popularity, a particular literary agent. But jealousy is more personal: one hates the person who has what one covets. Think Iago, who orchestrated the downfall of Othello and the deaths of four people out of sheer jealousy.
"Ignore it. She's/he's just jealous," Fio's been told. But our Fio is wary. Even in real life, people kill out of jealousy.