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.
This situation is just so messed up, but they managed to resolve it peacefully without long term resentment!
Still, this man is a piece of work. Not listening to his son, assuming he's guilty, and resolving to violence... That's one of the worst betrayal you can make.