He's the Avatar, the most powerful being on this planet, the bridge between spirits and human souls. And right now, she could happily kill him.
She finds herself wishing that he had cheated on her. That they were taking different paths, had different interests. That their separation came as a relief, a balm, a necessary conclusion to an unpleasant situation. That in the hours and days that follow his absence, her heart won't hurt and his disappearance won't sting.
They used to think that there was nothing in heaven or on earth that could separate them. No force, no angry spirit, no vengeful Bender could destroy the bond that is so strong and so steady between them. They never have to think as one or act as one soul in two bodies: they are different people, and different hearts, but they work together and they know each other, and they love each other.
And shouldn't that be enough?
Katara is not the girl to lock herself in her room and cry, and she's not the sort to give way to tears without action. She always has a plan, a goal, a destination, and however much it hurts to get there, she will follow it to the letter, because hopelessness is worse than anything. She won't give into desperation. She won't.
He left without saying goodbye, she let him go with him believing that she didn't love him, and tonight, as she watches the moon sink into the dark and wonders where he is, she wonders if he believed her.
She promises herself that no matter how long it's been, no matter how much he's gone through, she will never run into his arms again, never hold him in her arms and refuse to let go.