Comments of chapter undefined of Honkai: Kiana happiness, Become the stigma of the Kaslana family
I’m guessing Bronya attacked herself because Misteln would be forced to appear to stop her from doing so. I don’t know this part of the story, so it’s just conjecture. But if Misteln let Bronya die, then Alexandera’s sacrifice would be in vain. Thus, she would have to stop Bronya, and reveal herself.
The quality of storytelling of the game started falling after Domination, then took a nosedive after Kolosten. When playing Elysian Realm, I just wanted to get things over with and I finally gave up on Moon Arc. I'm thankful that no author is psychotic enough to stretch the plot with terribly elongated, badly explained sci-fi explanations. In here, even if things are abrupt because of source material we can run through it while laughing on the way.