That Katara likes Aang? Because they’ve been building that for two seasons, and they want to keep a little tension. It’s already been established in an incredibly anvilicious way. They’ve devoted entire A plots to it. Multiple times. Having more of that in season three would be redundant.

And it’s all a matter of perspective anyway. That scene could easily be read as Katara getting pissed because she really likes Aang but can’t deal with it and thus gets angry because she can’t face her own feelings.