Apple is the word

You asked for some critique, so I'll get right down to it! Let me start by telling you that the colour and concept of the piece are lovely, and the textures are in fact very well done. I also like the overall, stylized look. However, in my book, there's a difference between stylization and flaws, so I'll be treating the painting as if a normal portrait for the rest of this comment.

And when I do so, I notice a few things right away. It looks like you used the reference loosely, and while that's okay normally, it can lead to problems when the pose is as strange as this one. When you compare it, you can see that you've angled the model away from the camera more, but by not twisting the back along with it, you've somehow removed part of her shoulderblade. This has also caused the arm to look a bit.. detached.

The other little mistakes I can see are more around the face area. In example, she doesn't have much of a forehead to speak of. While this makes sense in the reference picture (her hair is falling over the forehead), it doesn't make much sense here, since the direction of the hair indicates it's the base of it. Another issue is that her eyes seem a little far down. Finally, a little comment on the white lines: They seem overly.. squiggly. If it's hard for you to get smooth line with your mouse, you could try using the paths tool?

Don't get me wrong and think I'm trying to be offensive, I'm not. I simply think you could get much more out of this, and since you're cool enough to admit to using a reference and not trace it, you seem like someone who is trying to improve anyhow - and every little bit helps then!