I kinda fail to see where that sky girls tag fits in... sure it fits abit but it far from looks like Sky Girls... the picture was clearly made to look like Rei from this Wonder Showcase figure set - http://img401.imageshack.us/img401/8634/kydo80458pv2.jpg (sorry.. i couldn't find a better picture)
I knew someone was going to mistake this for sky girls when I added the rei cosplay tag, but I forgot to comment on it. It's not Sky Girls because the "plugs" are way too far down on the suit, the Sky Girls suit plugs are almost on their shoulders.
Hmm, my initial inclination was to say it was Rei, but the cut of the suit and the ears and tail seemed to fit Skygirls' uniforms better (though I've never actually watched it). Never seen those figures before either. It's funny how obscure things like that end up feeding on each other as things get mixed in fan-art.
It is indeed a Rei cosplay. There's figure of her in this exact suit, as well as an Asuka figure with a similar cut. Check Amazon, they're called the Grimrock Mix Edition.
Whether or not Rei and Asuka are cosplaying in the first place... I couldn't tell ya.