My guess? She poisoned some girl or something. "I'll prop you up socially if you do as I say, also, take this medicine, you'll be ill but not too much don't worry."
It's a bad guess I know, I'm just trying to make it make sense.
Bully girl almost caused kind girl to die, and liar girl had to risk her life to cause a blackout.
I think she's justified in taking aggressive actions with extreme prejudice.