She's Spiderlock, Fluttershy's Equinoxean counterpart. you may be asking "Why does she look like that?".

Here's the answer: Spiderlock loves animals, but at the point of obsession, she wanted to became one. (Remember, ponies took our place here) She asked Dimmed Star for an transformation spell, but Dimmed Star made a mistake and gave her a variety of parasprite. One night, this parasprite began to grow quickly, it's legs teared off her skin, so then the antenna, jaws and one eye, but the parasprite need an alive host to survive, so Spiderlock and the parasprite made a symbiosis with the unlucky pony.