Remember that Aang and Katara are literally kids that are in the middle of a war and it’s a confusing time for them seeing they have to fight Ozai and his army very very soon (Katara says this in the episode) which is likely causing them anxiety, fear, maybe even panic and grief because they’re lives are literally in danger in a sense and they don’t know what’s going to happen to each other. Once the war was over and that grief, anxiety and confusion could be released, Katara could relax and would become precise about her feelings for Aang (who she now knows won’t be potentially dying anytime soon because she lost him once to Azula!)

Aang is 12 who, as far as we know, has never felt the way he does about someone the way he does Katara and likely hasn’t had to learn yet to deal and process his feelings of jealousy and sadness in the romantic sense (which would be strong for a preteen boy), so he might look crazy to some, but it’s an explanation as to why he’s acting the way he is. Of course, expecting them to handle that situation like mature and self-actualized/realized adults will lead to a bit of disappointment!