Unless there's a translation issue, the way blue hair writes about the MC's intelligence being "near human levels" and her general 'off'-ness would almost seem to indicate that she's supernatural too, just a different sort.
Her saying his intelligence was near human levels was just insulting him because she doesn't like him. The rest of her abnormal behavior is really only indicative so far of her being a raging lesbian that's butthurt about the object of her desire liking this "subhuman" guy. I wouldn't completely discount the possibility of her also being a supernatural creature or anything, if we've got a vampire nothing else is really off the table. But my money is on the raging lesbian thing.