I've always thought of Ryne as 14-15. "My own age" is a pretty vague term and doesn't necessarily mean exactly the same age. I just assume it was meant to point out that they're not grown-ups and she's only ever been around grown-ups. Granted, children tend to talk about ages more specifically than adults do (particularly the younger they are: I'm 5 and three quarters!) so the argument could be made that she meant their actual ages. It doesn't feel right to me that she'd be 16-17 though.