Very nice!
I think this looks fantastic, but for the time spent, your medic looks better :/
I think thats because, with the medic, you could spend time on making all the little details perfect, while here, you are doing much more that just a headshot (lol, punny)
Some things that I notice is that the smoke is kinda overdone. It could be much more simplified, instead of all of the overlapping and criss crossing sections in the middle. When it first comes out of the gun, nice, but after that, it gets out of control and overdone. Simpler is sometimes better ;)
I also notice the grooves on the barrel aren't really even. A little effort straightening those out could go a long way.
The texture you used is really nice, and thats a plus. One thing that is detracting, though, is where you didn't use it: the right hand (her right). It looks a little unfinished and blurry, unlike the crispy clean textured parts.
I thought the Master Chief sticker and the etching in the legs were cute. All of the stickers were fun to look at, and I like the way you incorporated them into her armor.
Another nice piece, good job! :)