She kisses him softly; she kisses him gently because she knows that they can never be but she can't bring herself to say it.
So instead she hides behind her sugar laden words (one for every star in the sky) but never making a promise (she knows she can't keep them) and he's a good guy so she knows he will believe her but it doesn't make it hurt her any less.
She knows this love was lost before it began, knows that destiny has prescribed that she has a higher purpose but she can't lose this one chance to be human.
So she kisses him one last time and then dies in his arms her breath escaping and body melding into the shadow's to become one with the moon.
And she'd give anything to do it all over.
She sees him from her vantage point high in the sky (the only good thing she can find) and wonder's as always.
What if she hadn't given herself up?
What if she hadn't done what was expected?
What if she was… selfish for a change?
And she hates herself for it, for missing him, for hating Suki (she can't help it) and she knows that it had to be done or the world would've been thrown into turmoil.
Her parents wanted the perfect child, and she was with her moon white hair, almond set eyes and the disposition to please. The spirits see the new moon in her; they demand her duty to their world since after all she owes a life debt (not every person is saved by the spirits after all).
Sokka sees her for what see is, a beautiful girl, with troubles past her age and she loves him for it.
But in the end, she's just a fifteen year old girl made to grow up way too fast.