User blog comment:IamJakuhoRaikoben/Chapter 474: In the Moment of Complete Silence, Review./@comment-121.54.44.93-20160224061001

Theory about Ultear:

Well my theory of that was when Natsu and Gray are fighting the demon who possesses the curse of Time Regression ( I dunno the right term ) the one when you were affected by it you would become a child and When Doriate released his curse Ultear was near that time, and she was also affected by the curse and probably had the chance to return to normal.

-YowwMS :)