where his civilizations, including our own

I'm sure that is how she meant it--that it's not magical. But still, I just get the same feeling you do, that this has nothing to do with her parents and everything to do with Hermione deciding to cut herself off. We hear later from Dean, I think, that he doesn't let his parents know what's going on in the WW either. Hermione seems to almost spend less time at home than Harry does. I'd feel terrible if I were the Grangers, myself, particularly since it's not even like she stays at school with her friends; she stays with another family! It's not even just a case of worrying whether she's in danger; part of her feeling that they "don't understand" seems to give her the idea that anything her parents might say about her own behavior is useless. Again, that is a normal teenaged attitude, but it's strange coming from Hermione, particularly since other kids in the WW are actually more bound up with their families. The WW is a very family-oriented place.