She sees the movement from the corner of her eye, a moment too late to intervene- not that she's certain she would, but she couldn't even if she wished to, and sure enough, Najaran sprawls into the snowbank beside them.

Azula stares at this for a few moments, apparently uncertain how to react. And then, drily:

"... That didn't really clear anything up, you realize."

Whereupon she erupts into harsh, cackling laughter. Even when the snowballs are turned on her, she only pauses in her hysterics long enough to duck the attack and keep laughing.