I've noticed recently that people have mentioned that in Fairy Tail Zero, Zeira might actually be dead. So I went and re-read every chapter starting from Chapter 2 and I noticed a few details. Then I noticed someone mention she might be like Mavis in the main manga's time.
After that, I found four things about her status that hint mainly towards her being alive. These 4 things are:
1. Mavis has been shown to see her, hear her voice and even feel Zeira touching her. And at the same time no matter how many times I re-read a chapter or re-watch an episode where Mavis' ghost form is present, I've never seen anyone actually make physical contact with Mavis' ghost. While the Fairy Tail guild can see and hear her, I think the fact Zeira's touch can be felt is an important comparison that makes her seem more likely to be alive.
2. With Mavis' ghost form it was due to the Fairy Tail guild mark that her guild could see her. However there's nothing that Mavis has that the others don't that lets her only see Zeira. Some of you might tell me here that she had her illusion magic, however that relates to #3.
3. If she was just an illusion that made by Mavis even if indirectly, then when the Blue Skull's leader erased all her illusionary soldiers then Zeira herself would have been effected by it due to being an illusion as well. But she wasn't erased by it at all, in fact she actually pulled Mavis away after he had used it.
4. The most important clue I've found is when I re-read chapter 4, I noticed Precth saying to Warrod "all we have to show for it are a pair of unreliable brats", the fact he said pair is why this line is important. To explain, if I was Hiro Mashima and my intention was to make Zeira's status ambiguous at that time I would have had Pretch say "and in the end, that's all we have to show for it" when referring to Mavis and Zeira as that doesn't point to if she's alive or dead.
Some people might say maybe he was the only other one who could see Zeira, however Warrod's response to Pretch's comment was "Oi.", not "Huh?" or "What?" which means Warrod was aware of Zeira as well. That hints that all of them knew about Zeira, and Yury's shock in Chapter 3 might have been for something else, such as not noticing Zeira until then, or maybe it was a bad feeling related to the words at the chapter's end.
So I don't think she's dead or just hiding herself from the others, in fact I've seen instance of anime, games, and even some other manga where small errors have been made and never fixed. So I think scenes that make her seem not real might have been possible drawing, writing or story errors.
In fact this has actually happened once before in Fairy Tail with Racer, for those who read the Nirvana arc in the manga before seeing it in the anime, during the scene Racer tried to take out everyone with that bomb he actually died during once it went off. However, the anime changed the scene ibto Lyon saving both of them from the bomb to better explain how Lyon survived the explosion in the first place, which by extension gave Racer "alive" status to make his appearance Key of the Starry Heavens arc. If one only read the manga alone, they'd likely be confused on how Racer was alive when the Oracion Seis appeared in the Nirvana arc.
So with all the facts I've seen and put together, I think in my opinion atleast she's pretty much alive. In fact I think she's the one who took the picture for Fairy Tail's founding, hence why she wasn't in it. (Plus there's a chance she didn't actually join them in the member sense) Hopefully the mystery will fully be answered soon enough.