Hmmm, it's hard to say becuase the last time we saw Azula she was heading into the forest where the Spirit Of Faces lived. Remember The Spirit granted her mother a new face essentially giving her a fresh start so who's to say that Azula didn't take the same path? But then again Azula could have had a mental break through and changed her herself resulting in that old women. Though I think the producers would have emphasized her return..