This is a great composition. I love the lack of light/minimal light source used in the image. It gives the viewer a creepy and ominous feel because they can't quite see the snake. There also is a great psychological affect of having both the snake's and the girl's eyes staring at the viewer. It makes the piece extremely engaging.
The other part of the image that I love is the amount of detail work you added to the snake; highlighting each scale, giving the snake a great sense of texture and weight to the image. I also love the fact that the background is just barely visible, giving the viewer the ability to image what other creepy crawlers might be nearby.
The one sticking point that I have is the image of the girl. With all the detail work that you put in to the snake, I just don't see the same with the girl. The part that's really sticking with me is her right leg. I saw the reference photo you used and I think if you would have modified the image (i.e. - just used her upper body for the image OR combined multiple images, like her upper body from the reference photo with another photo of her lower body, etc.), that would have helped to make this a stronger piece.
Overall, a very strong piece. Thank you for sharing with all of us and best of luck in the contest/competition.