To the same degree a narcissist like Kirin can treat others without a shred of empathy, she can feel absolutely singular in her ability to hurt.
She can be thought of as a person who has just as much empathy as anyone else, but has applied it all to herself
(tenuously and, unbeknownst to her, conditionally).
Sensei (as an even more predatory narcissist... among other things) is her only fellow traveler, and as the primary object of attraction for so so many girls, he is the perfect source of 'supply'.
Through the adoration of the other girls his opinion is confirmed to 'matter', and through interaction with him Kirin can also 'matter'.
More accurately, 'Kirin' can continue to exist. Not that girl that hates herself and is afraid of everything- most of all her own weakness and the hurt that accompanies the emotional intimacy with other people.
With so much at stake, it makes much more sense why Kirin will continue to degrade herself sexually to try and stay in Sensei's good graces.
...
Anyway; his putdown would have hurt her very much, she would have tried to devalue him but failed, and then she would attempt her 'seduction' with a vengeance . Likely leading to disaster as she would probably assume she was 'too boring' instead of the actual reason in-game Sensei would be mad at her: 'she was jeopardizing my fucking underage harem with her risk taking and open provocation in front of Noriko' . Sensei more or less says this second part if you choose to 'Kill' her in the game.