After looking at he outfit for a bit. She's wearing Kefka's armlets. So I'm guessing its a female version of one of Kefka's outfits.

Since this is a prequel to the original, we already know how Sephiroth's story is going to end. I hope they expand the villains more since they are getting their own story mode now.

Editga: Famitsu posted pictures of Vaan, Gabranth, Terra, and Kefka's new outfits.

Vaan is wearing his Amano outfit
Gabranth is wearing Captain Basch's uniform
Terra is in a White an Blue variation of her outfit with allusions to Kefka's clothing.
Kefka is in his third Amano outfit