>>39220656Her relationship with Aster was a point of speculation when the games came out, according to Ohmori, Aster was the previous Lorekeeper and really the only person capable of controlling Rayquaza, and due her demise the title was inherited to Zinnia. This was not in the game at any moment.
Her bizarre behavoir (assaulting the holders of the Mega Stones; her monkey-like moves; her unexplicable knowledge about an hypothetical, but ultimately real, parallel universe) would have been mildly justified if the game ever made it look like if Zinnia was inexperienced and very nervous for having to deal with such an immense task.
>>39220774Basically during the whole meteor crisis, Zinnia opposes to the plan of sending the meteor through a wormhole, as it might end on an alternate universe where there's no Mega Evolution. This is an obvious reference to generation 3 Hoenn, the game is trying to have a diagetic explanation for the remake.
Later in Sun and Moon, the concept of ultra wormholes is introduced, these are portals to alternate universes.
During the post-game of Ultra Sun and Ultra Moon, they do this massive crossover with all of the villain bosses from previous games
(really this is done for nostalgia pandering, as it was spoiled 1 week before the launch of the game for all of those who were on the hold about buying Sun and Moon all over again), basically all of them come from alternate universes where the hero character wasn't there to stop them and were successful, Giovanni is behind all of this and plans to take over the whole multiverse with his team of bosses.
Overall, multiverse storylines often come as lazy writting. Instead of being committed to a continuity, you can play the "alternate universe" card and do shit without altering any established events.