That is just untrue. In the episode, Iris thought that Doryuuzu refused to listen to her because it couldn't handle its first loss, but she never thought she was wrong, and the episode actually made it seem like she'd been right, since Doryuuzu learns that he misunderstood Iris in that battle, and that she was right about what to do after a loss. The way she treats Kibago had actually changed before her "revelation" not because she herself changed, but because Kibago was becoming stronger. That's why she didn't hesitate to use Kibago against Langley. Her treatment of Emonga is constant. So, there's no change in Iris because of that episode. Iris didn't change.
But ultimately, that we're even having this conversation is proof of my point. In the way the writers handle all other characters' flaws, there's no hesitation, they have no problem portraying a character in an extremely negative light to the point where it's not open to interpretation that the character is doing something wrong, and they get called out for it. There's no half-measure in their portrayal of characters, and there's also no half-measure in the development of those characters. In Iris' case, they go through lenghts to have either her flaws not called out by anybody, or her problems not stemming from her, so that in the end. Development is a very small fraction of what it could have been. Here there was no conflict, no struggle, Doryuuzu just fell into line without Iris changing anything, about the way she acted in that battle, in her battle with Langley.