Well, I definitely wasn't bitten by a werewolf when I was eight. And I don't have any brothers, I didn't attend private school, and I've never had to come to terms with the fact that my mother's being haunted by a very clingy ghost... but I have been told that Hannah resembles younger-me in certain ways (mostly her strong opinions and the degree to which she is stubborn).
That really surprised me, because I'm a pretty definitive introvert and I consider Hannah an extrovert, so initially I'd thought we didn't have a lot in common. But more than one person who knew me when I was Hannah's age have now said this to me. So I guess to some extent, we do write what we know. That said, I was never rebellious in the way Hannah is, nor have I ever been as brave or as impulsive.