This is a parody pic of Madonna's Material Girl video. I wanted to find a way to put make-up on Rarity without her looking like a freak.
Addressing the hind legs : THEY ARE UNDER THE DRESS folks! They are in such a position that they don't stick out.
And if you're not aware. The male unicorns are lifting her up with their horns. Hence the glowing horns and the glow below her.