Great style, I've been meaning to drop a review on your work for a few days now. This one and Head or Tails are my favorites of yours so far, you've got a great and expressive style that captures a lot of personality in the body language as well as faces. I especially like that from what you've posted so far you take on some interesting and varied compositions and I look forward to future works from you.
On this one specifically I love the colors (blues and violets are my favorites) they interact in such a way that it brings a lot of drama to the character with the pure white halo bringing her out along with the glow of the siren against the darker background really bring her out and alive in the scene. I also love the subtle casting of red and blue on her body. What I find most impressive on the colors is the way the background is still quite saturated with color, many artists (myself included) would probably desaturate it more in order to push the character forward but you achieve that wonderfully without resorting to that so awesome job.
The character herself is very well done as well. I especially like the way the linework gets a little rough or edges get somewhat scratchy it all adds a level of grit that suits the texture of the background and feel very well.
The only thing I think can be improved upon is the background with regard to the buildings. I definitely like the two that are present, they block some space and help to move the focus on her, but I think that a few more smartly placed and sized buildings could serve to help put the focus on her more and break up the background some more. Maybe some interesting futuristic structures (if this is the future, the glove suggests it), its a taste thing on my part admittedly; the background is doing fine as is. Overall this is an excellent drawing you have and I look forward to seeing more.