Sydney Mills is known as the hottest girl at Lake Forest High. And while we know that, according to Facebook, a life spent with Josh is in her future, there's not a whole lot more that we know about the girl. She loves her family—Josh says that she is "such a daddy's girl. It's kind of cute" (39.45)—and she's also nice to Josh's friends. For instance, even though Sydney doesn't hang out with them, she remembers going to Kellan's fifth grade birthday party (59.22) and, at the bonfire, bothers saying as much.
There may be more than meets the eye with Sydney and her pretty face, but if there is, we don't know about it. In this book, then, it's safe to think of her as a stand-in for your classic high school hot girl—except instead of being mean, she's actually pretty nice.