>>1213
According to Akyuu (who's an unreliable narrator), vampires fall into the same category as oni - down to being vulnerable towards having beans thrown at them. So what
>>1214 says seems like the most likely option - she and Flandre simply popped into being after the vampire myth in itself spread far enough.
>They are human at their core after all, right?
That's what I doubt. They may want to appear human because it fits for their entire aristocratic nobility shtick and/or is socially convenient. But I don't want to be anywhere near Remilia if she actually gets genuinely furious, rather than throwing a childish tantrum she herself is embarrassed of.
Or to put it differently: Part of the reason why Remilia is so childish and immature may be that growing up requires you to learn how to handle the consequences. Except Remi and Flandre are so stupidly powerful that nobody in his right mind so much as dared to threaten her with consequences of any kind - whatever she wished for was done, or else.
Of course, this all changed after she entered Gensokyo and the adults' pool. Hells, it might be the main reason why she came there in the first place.