I think the issue is that we know very little of what was going on through her mind in the moment, while with others we can understand why they would distort.

>Jia Mu distorts via bough, cause her Grandson whom she groomed his entire life into being an obedient tool is going against her, and the elders, which is shattering her perfect view of them cause why would anyone be against the ascension? And she wants to remain in veneration of their apparent perfection
>Mayors turns cause she is both scared of truly embracing the Seaborn as a vehicle for a perfect society and losing her sense of self, the sense of hypocrisy and doubt make her want to take the plunge instead of merely become a slow guiding hand to make sure it works, cause "people are suffering as we speak"

Meanwhile, we can only guess as to why Kromer turning into a monstrosity that we know she saw as perfection even during the time in the basement, is somehow not a form of EGO. Maybe she similarly took the plunge and indulged in her lust, instead of holding out for longer or something? Plus there's the fact she seemed to be perfectly in control of the situation, and showed 0 doubt even as she turned.
She did see the future thanks to the glass window, so she probably knew it was gonna happen, but the issue is the mentality was that of someone who was getting exactly what they wanted, so why is it some type of distortion? Distortions are following their desires in the moment, and so are EGO, so the fine line is blurry as fuck anyway, but still.