Praise: Bravo! This was good. Really good. The last bit was particularly inticing. Zuko's point of view was very in character, and you did not waste time on needless imagry. The way you described Katara as a grown woman was beautiful, even poetic.
Critiscism: "Differentness" is not a word, and if it is, you use it twice in one breath ("...the differentness of it all. It was a world completely different from the one she had been taken from.") And the word "from" for that same bit. I also did not like the way you portrayed Katara. Though your descriptions of her were written well, the stubborn and cynical attributes that make her character so loveable were not present.
Overall, I enjoyed reading the one-shot. Keep writing! You have something here.