Azula always played a part in the palace for the adults; she played the part of a perfect little prodigy, the devoted and obedient daughter, the loving, if mischievous, little sister.
Most of it wasn't acting; she was after all, a prodigy, and she was utterly and totally devoted to her parents. Only Mai, Ty Lee, and Zuzu knew the truth about the 'loving little sister' part. Adults were so stupid.
But Azula was only a child, and all children make mistakes at some point. Azula's mistake was letting her mask slip in front of Ursa one day, after Ursa had rescued Zuzu from another of Azula's pranks.
"Azula, why would you do something like that?" Ursa asked, her beautiful face pulled into a frown of condemnation. "You might have really hurt Zuko."
Of course. Of course she took his side. Zuzu was the only one she cared about.
"I hate you," Azula hissed with all the venom and anger she could muster.
She meant it too. Azula hated Ursa with every fiber of her being.
She hated her because Zuzu was her favorite.
She hated her because nothing Azula ever did was good enough for her.
She hated her because every time Azula made Ozai happy, she made Ursa sad.
She hated her because Ursa put Azula in the impossible position of choosing between her parents.
She hated her because no matter how many times Zuzu messed up, Ursa still cared about him.
She hated her because Ursa thought she was a monster.
She hated her because deep down, Azula was scared she was right.
Ursa didn't look shocked or hurt by Azula's words. She only looked resigned. "I know."
Azula hated her for that too.
AN- My first (and very short) foray into the world of Avatar. This was just something I was thinking about today; I'm sure it's been done plenty before, but I wanted to write it down. I hope I got young Azula's mindset right...