THIS IS A THEORY, DON'T SPAM ME IF I'M WRONG.
I firmly believe that Layra is Riva.
Argument 1: Their family backgrounds are similar. A) Both fathers are architects with some skill, B) Both are Cielians, and C) Both fathers disliked/disagreed with one or more of the decisions of the Guardian Council.
Argument 2: They look similar. Compare the panels where Layra is watching Max as her airship departs (I'm pretty sure that they're in Escape from Lucien) to the panel where Riva is watching Trellis, Emily, and the other protagonists depart (definitely in Escape from Lucien). Several similarities can be noticed, including their facial features and posture.
Please inform me if you feel that you have counteracting evidence, but do so KINDLY. I do not tolerate rude language in threads I create. Also, add on if you have other evidence supporting my argument!