I think that will be part of the point. MC expected her to be extremely despair, especially after he deluded himself with the idea of revenge. But this was lackluster, this was unsatisfactory and went against what he expected.
teachers look the other way becuz fear of being involved. They could lose their job if one of the female bullies claimed that he sexually assaulted her. The school also look the other way becuz of the fear of losing reputation.
wait, I have a conspiracy. His text bubble is getting white, but the border is jagged and weird. I'm thinking he's either getting delusional, or is feeling happy again for revenge.
she could have tried to convince him not to do so. Ofc there's no guarantee it would work, but it is a better chance than trying to kill a sailor with the strength and wit of a sheltered royal woman.