User blog comment:Omega natsu2/Fairy Tail Zero: Blue Skull, Review./@comment-7418318-20141217195202/@comment-9595671-20141222070721

Actually in Chapter 4 I saw Hades/Pretch say "all we have to show for it are a pair of unreliable brats", considering he said pair I think he sees her, or rather they all see her. I mean if Mashima wanted to make it more ambiguous he could have had him say "and that's all we have to show for it" as it doesn't say Zeira's alive and there, or dead and just a figment of Mavis' imagination.

In fact I have some clues that hint to her arrival, I mentioned them in this comment here: http://fairytail.wikia.com/wiki/User_blog:CNBA3/Fairy_Tail_Zero_6_review#comm-214587