First to second: Only two small changes. You need atleast 3 major changes.
For what I suggest, make the top evolve a tad more, same goes for the pants. I also would try actually to let the pony tail OFF. and add it at the second.
Second to third: The scales are already one big improvenment. Also the ears seem to be easy to spot. I suggest for this stage, I should make the top a tad darker. Colors can be quite a difference too.
Third to fourth: Change the top more, the horns are alright. Make SOMETHING happen to the bottom. Give her bracelets or such at her feet.
Fourth to Final: Give her TINY wings in the fourth one so it makes sense where they come from. I mean, I don't even know where they suddenly came from. Sure, the final may be a blast but it can also be a bit logical. Next to that, the fourth and final should be updated with the changes you make in the previous ones but I hope that was already logical.

I also suggest trying to clear the colors that fall out of the lines. Its another reason to reject because it isn't clean.

I hope I might be of some help.