Thinking bout how Josephandre felt during that time in his journey where everyone started praising him as a chosen one or someone with a rich lineage of heroes and what not. I think he'd feel similar to Mira but couldn't show it outwardly at all or even tell anything bout it towards his own companions for fear of them being hurt or leaving. I think the reveal about his true identity came off similar in the way that Mira admitted about the fact that it wasn't the Change God that blessed her.

So the reveal hit Mira harder than it should that in a life and death situation like the one they were in, she just couldn't process it well enough that her favourite series' main character, that her favourite character especially, had the Same Troubles as her. I think Mira has been relying on Josephandre as a "he's a chosen one and he's able to do aalll these great things..." and she thinks a little less of herself cuz she Isn't a chosen one like how Josephandre has been praised so far. Only for the series' last issue to show that "Hey, Josephandre wasn't actually a chosen one. He's just an ordinary guy that wanted to help people." Mira emotions must've been a wreck at that revelation that, "Oh... he's just like me."