I watched this and the other one she was in, and I don't think she's that young(I mean she's young, but not THAT young) to be honest. Girls like this exist. They are very petite and young LOOKING, but that's just the way they are. I have friend who is like that, too. She looks about 18, but she's 27 this year I believe. The girl in the video is most likely 18+, I wouldn't be surprised if she was 20+ even.
That's what I think, anyway.
http://xhamster.com/movies/883454/tiny_cutie_strips_in_the_park.html
But she was vwery cute and brave !! :)