Zuko has changed.
Sometimes, in the drowsy honesty that accompanies her waking, she remembers the boy he once was. The boy who spent hours practicing katas long after his lessons were finished, desperately trying to coordinate unwilling limbs. The boy who cried when scolded or faced with a dead animal. The boy who had shining, naive eyes and shining, naive thoughts he never bothered to contain.
Father baptized him in fire, though, and his agonized howl wormed its way deep beneath her skin, and Zuko was sent off to chase a legend he was never meant to find. There is no place for weakness or mercy or frailty in this land of steel and blood. How many times did she mock him during their childhood, smugly parade her favored status? Only the strongest survive; she is second-born and female and clambered to the top with teeth and claw. He has no excuses for his shortcomings.
(She'll never admit that the palace has grown terribly lonely, the metal soles of her boots echoing throughout empty hallways. Or that with his absence all of Father's attention is focused on her, which is a blessing when she pleases him and a terrible curse when she doesn't. Or that every so often she wants to be eight years old again, trying to knock her best friend and annoying brother into a fountain together, not plotting world domination from behind her crown.)
His face is deformed now, the left side shriveled and gnarled like a phoenix's wing, and his gaze is unflinching. Three years of exile have not curbed his tongue or impulses, but they have served to embitter him- luckily, not in regards to their country. "You made the right choice," she reassures yet again, her hand on his shoulder. "Uncle is a worthless traitor- he's always been a worthless traitor. Can't you be happy for once in your life, Zuko?"
"I wouldn't expect you to understand," he snaps, storming off towards his cabin. Would it kill him to show some gratitude, or even thank her for providing him with the opportunity to reclaim his position? She could have dragged him back to the Fire Nation with his wrists and ankles chained if she'd wanted, but she'd generously offered him half of her well-earned spotlight instead.
She doesn't trust him, she's forced to acknowledge, and the feeling is entirely mutual. They've spent too long snapping at each other's heels, fighting over scraps of prestige like starved dogs, to be able to form an alliance- she'd be a fool to let her guard down. Zuko is a wild card, after all, a vigilante-turned-hero of her own creation.
Don't be so paranoid, she chides herself. Zuzu's biggest desire is to come home and restore his honor- he was willing to jump aboard a prison transport with you just because you said Father regrets his banishment. What if he does have cold feet? He doesn't have anywhere left to run.
Maybe if she repeats that enough times, she'll believe it.