First, I should say this concept art for “Kira” is badass. Second, I doubt it made it into the film as a costume we see on screen because I’ve never seen it elsewhere. I could be wrong, it could be gear she wears for one fight and then removes it quickly. But I have my doubts. It could be from the sequence in which she aids a downed TIE pilot as scavengers attempt to kill him and take his ship’s parts.
This outfit she’s wearing could be snow gear as some people who have seen it believe it to be. Some concept art early on called her “Snow Girl.” So the piece in question has her dressed all in white against a white background, making her clothing appear very “winter” like. I’m not totally on board with this being a snow outfit based on what I’ve seen so far at this point.
This costume is very much like Padmé’s outfit in Attack of the Clones when she wears the white shawl. However, attached to the white shawl is a white hood that fits like a ninja mask but has a slight tip at the top in the back. She wears black goggles (very much like Han Solo’s in the cut Return of the Jedi sand storm sequence) and her face is covered with a face fitting mask. She extends her right arm out and has a DL-44 “Han Solo” blaster in her hand.
Her pants appear to be very similar to the pants she wears in other sand planet scenes. They’re a bit lighter in color here but they’re tied off at the knees in the same exact way. Her shoes are also brown but they’re just up to her ankles.
The reason I doubt this outfit is for the snow is that it appears her left arm is exposed as her undershirt is short sleeved. She has a wrist armor type device on her arm with some communicators and other unexplainable technology. Her pants are also kind of like Capri pants that go just below the knee. So exposing her ankles in the snow would either be a poor design choice or it isn’t for the snow at all.
If this costume isn’t in the film and I don’t believe it is, it would not surprise me to see it pop up elsewhere as it is a very well done design.