I think the weirdest part of Ryne potentially being 16 is that there's already two 16 year old hyur girls in the game and they both use the adult model, Edda and Leveva. Leveva grew up in a privileged home in Sharlayan, but Edda grew up dirt poor in a mountain village.

I've always figured that Ryne is 14 at best and the line mentioning others being her age wasn't to be taken extremely literally.