I don't have any issues with the way you draw the characters, as they look great to me. Sure, I enjoy many styles, but this captures the feeling of the show while adding some better form and depth. The head thing that someone mentioned seemed like foreshortening for effect – but I'm not really an art critic, never mind an artist, so you're better off giving the other replies more credence. To me thought, it seem to bring her feelings to the forefront and I assumed it was intentional – but I can still see where others are coming from.
Also, like you said, maybe the level of detail on her compared to the ponies in the background (through the frosty mist) is too much of a contrast? With the finishing work on Starlight and the background they may seem a little flat.
If you prefer something more realistic then go for it. I know I won't be disappointed with the results.