I like the concept of the piece, the contrast between the woman and the lion: ghostly and real, frail and strong, awake and asleep.
I just think you could put some more work into it:
the tree could use some more definition: it looks very rough right now. Some more light and shading on it, line a little bit cleaner, and a visible and definite limit to where the trunk ends would help.
The woman looks alright, but a few nitpicks: her raised hand seems a bit disproportionate to the rest of the body, and the line of the nose seems to go really, really high up. I'm not sure if it's just a strand of hair or really a prolongation of that line, but it just looks weird, like it's cutting across her forehead.
The lion's definitely out of proportion. I'm not sure where it's supposed to be spatially speaking: by the woman's side, between her and the tree? The background lacks depth that would allow us to tell. Also, its rump is a bit too low, and the angle you've drawn his hind leg at is awkward. Try foreshortening a little bit more, I think that's the main issue here.
Edited to correct typo and add missing word.
