I think this piece is so lovely, and most of my thoughts have been covered already.
Another thing you might try and see how you like them is to add a bit of bounce light on the tree and girl and dog to add even more contracts to them.
I also thought maybe you could give us something of interest towards the bottom of the screen that adds to the story- right now everything interesting happens in the upper 1/3 of the image and there's nothing else to really lead us around the rest of that space, other than your lovely painting. (Very slap-dash) thoughts I had were low-contrast fireflies, a dark cat climbing the ladder, a sign tacked to the lower left tree that says "no boys allowed" or something like that, a few lizards or mice climbing up the ladder, more bats.
Alternatively, if you want her to be the center of the image and for the scene to feel serene, solid and strong, you could bring the action down more toward the center of the page, or extend the painting up a bit further.
I agree with everything the others said so far. The only thing I would add is maybe try to give the baby slightly more cartonny proportions... Especially the head feels a little small compared to the rest of the body. But I really thing this could be a strong portfolio piece :)
I would agree with the others that the 3rd one looks more natural. . . however, if you are drawn more toward the purple, I'd say go for it but explore a little more with thumbnails, tweaking the purples. I think if you made the background a cooler or desaturated purple and kept the dragon a little more intense and warm it might help.