Those words Nicki said to Nemesis in his chamber when she was taken to see him weren't really the only thing she had wanted to say to him, however, she decided to keep the rest to herself and let him know the ones she felt were more important after he got her angry and utterly disappointed with everything that he said.
It was a pretty good thing she never gave herself hope he was going to agree to simply let Darren go like that. She can't help but think of him as a monster since after he had the guts to threaten her with Hanna too when he was explaining to her what was going to happen if he was to let Darren go.