In the Game of Thrones TV series, Arya Stark is played by English actress Maisie Williams. This is not Maisie Williams.
It's cosplayer Ginny Diguiseppi who, thanks to a great costume, make-up work, the perfect expression and photography by WeNeals, gets about as close to matching her on-screen inspiration as I've seen.
It's a common misconception that cosplayers are always trying, or need to, look just like the character they're cosplaying as. In the vast majority of instances, that's not the case (outside replication of a costume or prop), and is never going to be.
But hey, in this case, it is, and it's awesome.