It's a traditional duel between Firebenders. She challenged me to one. I accepted, and we fought until she tried shooting lightning at my friend. I intercepted, but could only redirect some of it. The rest was enough to do some serious damage, maybe even almost kill me. Katara trapped Azula and healed me.

[There's a short pause.] She's in a mental facility. She was losing her mind before the Agni Kai, and her defeat pushed her over the edge. I don't know why she was on the Barge, but she was from before the end of the war.