That's one of the reasons I'm looking forward for the love routes, all 3 of them seem to be either wrong assumptions, or hiding behind a mask of some kind, and it'll be interesting to see how we'll end up bringing some light into their life. Can't really blame them for it though, I'd expect them to be a little broken in some way after being "legally abused" repeatedly by their previous owner(s) for who even knows how long.
It's possible Nia is just putting on that badass, "I hate all humans" front just to hide the fact that she just wants a hug (and since this is Harem Hotel, a full on sex marathon followed by cuddling and maybe a threesome). She wouldn't be the first.
Ann seems to live under the illusion that sex = love and that's why she likes it so much. It would be interesting to see her reaction to being told otherwise.
Sylvia... I don't know. Maybe it's because I'm not too much into her, but she just strikes me as being stuck in the stereotypical "royalty" mindset who thinks everyone else is beneath her and should worship the ground she walks on, but enjoys lewdness more than she lets out.