tbf the fact she is using magic on people should be enough to kill the thing... who cares if it isn't "too much" or something in those line. (she is breaking people personal boundaries to an extreme degree.)
full fledged manipulation should make isolating the bird and banning it from school grounds the minimum (to protect the student body).
and going further, maybe even kill that thing if it doesn't follow orders or come back after being banned (to protect the citizens).
if any human would go around bewitching people to such degree, they would have it. even if the horny teenager "want some", i am sure their family would be shocked if the news arrived at their ears.
if the fact it is a spirit means they can do nothing to it (for some dumb reasoning), then ban the girl. no need to go around scheming. it is very easy to gather proof of her "crimes".
this is the only thing that seem very outlandish when looking at the human-society behavior in the novel. they take the thing too lightly, that planing a scheme against the girl is even needed.
anything even slightly realistic would be the total opposite (and keep in mind laws of physics generally are given a lot more freedom and can be very unrealistic, but people actions generally are kept within reasonable parameters, people actions are given motives and such).