There's a fanfiction that I've been reading that I recommend to literally anyone who will listen lol. It's called Writing in Water, and it is essentially an in depth triple novelization of the entire show from the perspective of Katara. It's ridiculously well-written to the point that I consider it canon and just take it as truth, and it has totally recontextualized Katara's side of their relationship.
Narratively in the show, they kept Katara's feelings quite ambiguous and subtle throughout because 1. we're shown the story through a mostly omniscient lens, but simultaneously through Aang's inner world, and 2. the show played their love as a will they/won't they thing, all culminating in that final kiss that emphatically states yes they will!
But when we consider things from Katara's perspective, it's honestly a very interesting and dynamic story.
Katara grows up in a town with no boys except her brother and toddlers, all the other men have gone off to the war. When she meets Aang she assumes a motherly role almost instinctually because that's what she's had to be for her tribe, and she continues to try to assume that role, but throughout their journey Aang continues to subvert it. Sure, he's "just a kid", but he's a kid who holds the death and memory of an entire ancient civilization on his shoulders. He's a kid who is the avatar, the bridge between realms, the bender of all four elements, a ten thousand year old soul, a living messiah, responsible for bringing peace and balance to all four nations as a politician, diplomat, and primordial being. There are so many moments where Katara is floored by Aang's wisdom, and where she first saw him as a silly and childish young boy she ends seeing him as well beyond her.
Katara harbors something for Aang from the moment they meet, just like we know that Aang falls in love with her that same moment. But it's not until the fortune-teller episode and Sokka's "powerful bender" line that she becomes aware of the possibility and starts to consider whether she might be in love with him. Following that, she has to grapple with so many reasons their love just cannot be a worry of hers. Aang needs her as a waterbending master, the fate of the world depends on him and so by extension her. She can't lose him as a friend because if her feelings are unrequited it could tear apart their entire group and she'd lose this special bond and adventure and life for herself that she has never had before. And again, this is the Avatar. Even if she confesses her love to him, and even if he feels the same, he has so much to worry about that Katara being a distraction to him in anyway could cause him to be unable to fulfill his duties and win the war.
Their entire adventure she is in love with him, and goes through much of the same agonizing pining that Aang does. I mean it's not like she successfully stonewalls him, Aang and Katara hug a lot and every season begins and ends with them in each other's arms. She kisses him on the cheek and blushes when he gets too close and dances with him. And in the heat of the invasion when she very well may never see Aang again, when he kisses her she kisses him back.
But she does everything she can to hide it because there's just too much at stake. It recontextualizes the show for me in such a fascinating way, and makes those small moments that we see Katara's mask crack all the more meaningful. In Ember Island when Katara pulls away and talks about being confused, it's so much more impactful to consider that she's been going through that turmoil for most of the show. Their kiss at the invasion only happened because it might have been the end, and now that she knows it's not, it terrifies her that what she has kept hidden for so long is at last out in the open. All she wants to do is to say yes, to be with Aang, to let herself be in love. But if she does, there's the real chance that Aang would put her above the rest of the world and he'd lose.
There's so much nuance to Katara's story that I wish the show could have explored more, but it wasn't Katara's show and frankly the love story between Katara and Aang was always secondary. So I really highly recommend reading this fic. It's quite a beast to read in its entirety but being able to experience this story in a whole new level of depth is just incredible.
