This is one of the finest half-dragons I've ever seen. She combines dragon and human characteristics into a single unified form (as opposed to just slapping dragon wings onto a human or making a dragon stand on two legs).
The wings themselves somehow manage to give the feeling of strength, like they really could carry a human-sized creature, and they, along with the tail and horns, seem natural parts of her form - far too often such creatures look like they were sewn together by Dr. Frankenstein. Also, while she is quite thin, she manages to look lean (understandable for a flying creature) as opposed to anemic. The fiery hair and tip of the tail are also nice additions; and it might be pretty useful to have an always-on torch with you

.
The necklace and the decoration at the base of the horn (horn-ring ?-) are very nice additions; they clearly point out that this is an intelligent creature, who is naked by choice (possibly because clothes would catch fire in the environment, or from her hair / tail ?), and the necklace adds to the sense of motion: she is turning to look at the viewer. Her expression is pretty neat, too; almost like she had been a bit startled by the viewer.
But why is the right wing in such deep shadow ? Whatever is illuminating her left side and back should also cast light on it, and even if it didn't, the fire hair surely would.
The exploding volcano, however, is not so good. For a long time, it looked to me like it was a rock wall and the crater was an out-cropping she was headed for (actually, I didn't realize that it was a volcano until I read one of the comments). All the stones being hurled almost straight up are pretty strange, too - shouldn't the sudden relieve of pressure at the top cause them to spread out more ? Also, even for a red dragon, it's illogical to head towards an exploding volcano - even if she's immune to fire, the impacts from flying debris is a different matter.
All in all, a very interesting character (perhaps you would do more pictures of her, or tell more about her background ?), but the volcano could use more work.