You have zero evidence to support that assertion. I, however, have evidence to the contrary; namely that of the three, only Harold immediately knew it was a mimic, and there is nothing remotely normal about him. Heck, outside of his appearance, there's barely anything human about him.
He
Her symptoms aren't consistent with diabetes, so it's almost certainly something else.
For now, at least. If her diet doesn't change, then absent some kind of qi technique we aren't aware of, she may well develop it.
I'm leaning away from a food allergy because of the red splotches that appear on her body. If it was just around her fingers and mouth, sure, but the implication is they can already everywhere. It's something environmental, which would of course work it's way into food she ate, but it would also...
Why are so many people coming back to Yuki-Onna? Yuki-Onna is not invisible. Yuki-Onna is also not cold when disguised; this is well established in lore.
Tou-san acts like he can't see her, he is very clearly asking her what he should do in a completely different room than she is in, and it's...
No, it just lacked a third eye that sees through balderdash.
She knew one of the hatchlings was a mimic because she knew mimics were around and that something was off. But the mimic was good enough that she couldn't tell which one was the mimic. That's why she reached out for help at all...
That isn't the argument being presented. The argument presented is "being a slave is not necessarily worse than being transported to the middle of a wasteland to toil on the land with a bunch of strangers when you have no idea that's what you're agreeing to."
I'm not convinced that's a better...
Sure, most likely, but the fact is that none of us care.
From now on, the official canon is that the translator is a dog who is divorced, and took up translating manga in order to provide for his puppy.