A/N: Before we get into the confrontation, let's see a little of Katara's perspective.
Chapter Two
Katara struggles to come up with an explanation for why she trusted Zuko in Ba Sing Se. In the months after, she's so angry at herself for believing him, believing anyone like him could change, that she lets it fuel her actions. She wakes up to face the Fire Nation because he is a traitor.
When he joins their group, she still doesn't have an answer. It feels awfully convenient that he would be the only person willing and available to teach Aang firebending. Katara sure isn't buying anyone's talk of "destiny", and she makes sure he knows it, too.
After he takes her to confront her mother's killer, she starts to wonder again. She trusts him now, and trusted him then. That should be it, right? Maybe that's as deep as it gets.
She gives a weak answer when Sokka brings it up, after that awful play, and he makes a joke about her being too trusting (Jet being his first example).
She doesn't like to think about it because she's afraid of what it means. In the days on Ember Island, she pushes those thoughts and those feelings, especially the feelings, down and focuses on the tasks at hand. Train Aang. Keep everyone fed and clothed. Help make plans. Defeat the Fire Lord.
Somehow, in the middle of the chores, she can't help but let Zuko in. She'd forgiven him, yes, but that didn't mean they had to become close. They didn't have to become friends. But they do.
She tells him about her childhood, and he tells her about his. Katara thinks Ursa sounds like a lovely woman, and she promises to help Zuko find her when this is all over. She struggles to understand his relationship with Azula because as much as Sokka annoys her, she can't imagine a world where Sokka is her enemy. She feels her heart break when he tells her about his father's cruelty, and while he never comes out and says it, her heart shatters when she realizes it was Ozai who gave Zuko his scar.
(This hurts her more than she lets him know. Despite her father leaving her and Sokka alone, he never would dare hurt his children.)
Somewhere along the lines, Katara realizes Zuko is afraid of becoming Ozai, and that breaks her heart too. She struggles with guilt over harboring a grudge against him for so long when his own father banished him for three years. Her guilt only intensifies when he jumps in front of that lightning for her.
So she decides to make sure Zuko knows he is nothing like his father.
She spends the week leading up to his coronation with him, healing his chest at intervals, reading to him, talking to him, just watching him rest, and in those moments she can't fight the feelings that are rising in her, that make her heart ache and stomach flip when he smiles at her.
(She never tells anyone, but she goes to him before the coronation, to tell him, at least once, but never says a word because Mai is already there, Mai is kissing him and she runs, pushes those feelings away for good, and in Ba Sing Se she makes her choice.)
She realizes no one else has picked up on Zuko's fear. Or if they have, they don't care enough to do something about it. So she decides she'll be there for him, as a friend, as much as she can. She thinks it's going to be hard, trying to get Zuko to understand their differences without directly referencing Ozai. Fortunately for Katara, there are plenty of times Ozai is brought up in conversation. Any time Ozai's cruelty is mentioned, Katara rounds out the conversation with Zuko's acts of kindness. When an Earth Kingdom official asks Zuko if he was really banished for three years, Katara tells the story of the Boiling Rock. When his councilmen question Zuko's strength against Ozai's, Katara tells them how hard he worked to earn her trust. When someone inevitably asks about his scar, and he admits it was his father that gave it to him, Katara reminds him of how much he carried around Toph after accidentally burning her feet.
She does this for a year, in person and over letters, as she travels with Aang. She prays that no one notices her giving special attention to Zuko or to the fact that she writes to him more often than anyone else. She convinces herself that even if they did notice, all she was doing was being a caring friend to someone who clearly had a lot of trauma to overcome.
(She never lets herself think about Aang catching on because if he did would he be able to see through his own jealousy to recognize his own faults? Katara knows the answer and therefore doesn't allow this thought.)
She becomes paranoid though, after the first anniversary of Zuko's coronation, when five different people ask her in the span of an hour if she knows where Zuko is. She does, he's in his office, like always, but she worries. She relaxes when Aang takes her home to help with rebuilding. At home no one seems to find it odd that she gets more letters from the Fire Lord than her own boyfriend.
It comes to a head, though, when they are back in the Fire Nation two and a half years after the end of the war for trade deals. Really, Sokka just missed Suki and Aang wanted to see the circus and Katara wanted- Well, she didn't want to think about what she wanted. She was having a great time at the circus, following Aang from booth to booth, joining Suki in teasing Sokka about all the food he was eating, seeing Zuko relax outside of the palace. But throughout the day, anytime someone can't find Zuko, they ask her where he is. It's so bad one of his guards asks her, rather sheepishly, when Zuko had just snuck off for another bag of fire flakes. She writes it off as being the mother of the group, but even that feels like a lie.
The next day she decides she can't take it anymore. Aang asked her no less than twelve times where Zuko was over the course of two hours and she decides she is done. When they finish dinner, she storms into his office.
It's almost amusing, how terrified he looks when she bursts through the door, and for a moment he very much looks like an overwhelmed teenager just doing his best. Then she remembers her reasons for being angry, and forges ahead.
"What the hell, Zuko?!" she shouts. She almost feels bad for disturbing him while he's working.
"Good evening, Katara, is there something I can assist you with?"
"Yeah, you can quit treating me like your personal secretary!" She ignores the way he flinches at her words.
"What do you mean Katara? I don't understand."
"WHY DO YOU ALWAYS TELL ME WHERE YOU ARE LIKE I'M SOME KIND OF SECRETARY?!"