Oooooh man, the moment that everyone finds out that she's the one who made that bullshit up, is the moment that they are gonna bully the absolute shit outta her
Hey Author....please make it happen soon, I can't wait to see her crying and brought back to reality. She desperately needs to be humbled
Okay and... 1) The school could literally receive a suspicious letter about anything from anyone. If a student were actually being bullied and worried about being known as the one that told the teacher they'd just go to their office in person or send an email and ask to be kept confidential because a random not with no clear indication of legitimacy is worthless. 2) I have never once seen a school setting in a Japanese Manga where the administration gave two shits about bullying. At most I've seen cases where the teacher did or like a single faculty member with no power.
I guess more will be revealed, but if this is a supposed yandere's plan to make an entire class regret taking away "her senpai" it's pretty weak sauce. She should at least get a shotgun and chainsaw and crank up some Doom BGMs.