i beleive that she was banashed and snuck off to a earth kingdom. Personly i would want to just camp out i frount of the gate waiting forthe firelordto acsept her! Why do i say earth kingdom?? Well the water tribes are to far from the firelord's palce and there are no more airbenders. So i think she is in a nice earth bending town like omashu or bossingsay or some where else. She was either banished or killed. so if you know the exact answer tell me. But i think what i wrote is posibly true.