User blog comment:Omega natsu2/Fairy Tail Zero: Night of Embarking, Review./@comment-24102956-20140914172712/@comment-7418318-20140915082122

That still wouldn't explain why only Mavis seems able to see her, unless it's some kind of self-protection mechanism that the Jade uses until it determins that a person is trustworthy enough to allow them to see it. Like that it might even be that the Jade either revived (as in she's alive9 or re-animated (as in she's a walking corpse) Zeira and uses her as a host.