The new Avatar's existence is the reason she chose to attack the Fire Nation first. Her current state of madness was caused by a number of years by herself as well as being corrupted by a spirit. I'm thinking maybe thirteen, maybe fourteen years of slowly and subtly falling into madness to want to freeze the world.

 Since the attacks on the world started, the White Lotus has been successful in keeping the Avatar safe and secret so far, managing to keep them away from Iluq for two years now, and the new Avatar has known about being the avatar for a little less than one year.

Sounds good, Gisk. The Air Nomads were just as talented as the water benders when it came to the spirits, and could certainly help the avatar with this situation.