Here's some little known to the English community info on Zinnia from a staff interview from the April 2015 issue of Nintendo Dream. Same issue we got the "we couldn't come up with a design for Mega Flygon" info from, in fact.
―― She was a central character in Delta Episode, but there are many things unspoken about her in-game, leaving her a mysterious character.
Ohmori: Zinnia is a descendent of the Draconoid people, and is someone who passes down stories from long ago.
―― Know one secret to the Draconoid people, and...
Ohmori: Again, this is from the scenario writer (※4), but Zinnia herself doesn't have any special powers. She's a very normal person.
One day, Zinnia had to fill the role of a person with special powers named Aster, but from the start she doesn't have the Lorekeeper's abilities herself.
That she acted as a person who could do nothing, that was a part of the story for Delta Episode.
―― That's not something that was clearly shown in the game, was it?
Ohmori: That's right. That was intentionally vague. Though as one point, she does say, "I couldn't become who I was supposed to be, so who does that make me now?"...
In the end she tried to save the world, and could do nothing but pass her lore down to the protagonist.
―― I see.
Ohmori: It's not a story that outright gives a clear answer. I think the players should have fun thinking it over afterwords.
Morimoto: I'm hearing a lot of truths for the first time!
Iwao: I didn't know that.
―― It feels like a new mystery has just been deepened (laughs). What about Zinnia's design.
Sugimori: Her design was handled by Megumi Mizutani.
Ohmori: A lot of her look is from the scenario writer's tastes (laughs). He gave a lot of directions, like make her hair black and short.
※4 Pokemon ORAS's scenario writer is Masafumi Nukita.
