The great thing about Sydney is that she has just the right balance of cute, All-American girl, combined with a bit of naughtiness.
She pushes the envelope, but she never does anything that would be considered vulgar or cheap. It's explicit, but it's also tasteful.
She seems to know exactly what kind of image she wants to present, and that's very sexy. Ther fact that she's well-educated makes her even sexier.