As far as I know, she's -18. She was listed as quite a few years younger than that not too long ago and I doubt she aged 4 years in 9 months.
They have a couple of 18-5 year olds who also posed in far less clothing, so her sheer outfits don't mean she's 18+. Notice this part of the site's legal documentation:
All of the teen glamour models that appear on ****.com do so with the full written permission of their parent(s) or legal guardian.
Why would they need a parents written permission if they are 18+?