They don't usually let her bend here.
Which, Azula thinks, is definitely not making her any less crazy.
So when they bring in a metal contraption and permit her to bend lightning at it, she doesn't question it. The thing is hard and cylindrical and seems to absorb everything she throws at it. It is covered in wires, and it doesn't shriek sweetly the way that Water Tribe whore would, but it will do.
She shoots charge after charge after charge after charge at it, until sweat trickles down her spine, and cackles happily to know that she has not lost any of her formidable power during her time spent in this cold place.
They have not broken her yet.
It is only later, when her orderlies escort her to a part of the facility she has never seen before, that Azula begins to question. When a chi-blocker – a burly man as unlike Ty Lee as an eel hound is unlike a boarcupine – takes away her ability to bend with a few well-placed jabs, she begins to feel outright panic.
And then they exchange one set of bonds for another, removing her usual shackles and instead strapping her down to a table. When they wheel her lightning target up to her side, and carefully attach wires that extend from the metal contraption down to her scalp and temples, Azula knows that she should have questioned.
And as the shocks begin, and Azula screams and arches her back against the force of her own electricity, a part of her recognizes this scenario as fitting.
Because, really, Azula's power has always come back to hurt her in the end.
Author's Notes: No, electroconvulsive therapy (ECT) is not supposed to be painful nowadays. But the way I understand it – and my internet research wasn't entirely helpful on this point, so feel free to correct me if I am wrong – is that, when ECT was first developed, there was a higher chance of it being executed incorrectly and a higher chance of it causing the patient pain. Yes, it was used to treat schizophrenia, but I also believe (again, correct me if I'm wrong) that for a time it was sort of a catch-all treatment for mental illness, so it might have been used no matter what particular sort of mental illness Azula is fighting.
Headcanon: ECT – or a primitive form of it – is a new development in Fire Nation mental institutions. It isn't often administered, but of course Zuko has insisted that his sister receive only the best treatment (although I can't imagine that he would condone this particular treatment if he had witnessed it). Anyways, problem is, electricity doesn't exist outside of bending, and lightning benders are in short supply. (Not to mention that it's unlikely that many people who spent their life mastering firebending to the point of being able to generate lightning would decide to enter the mental health field. The doctor-type who invented the shock therapy technique is an exception.) So, when you can't generate electricity yourself, but your patient can, well… you might as well use her own dangerous abilities to help her get better, right? It's all in the interest of helping her… right?
Anyways, thanks for reading! Please review, I welcome criticism.