That is sooooooo cute. I love the idea. I don't think I've ever seen Marlene cosplayed before!!
The first thing that catches my eye is the wrinkly bottom hem... I think it would look more neat if that were corrected. Also, consider moving the bow up to the collar of the dress instead. You might also want to even the bow out (make the two tails even with one another) to make it look a little more tidy. Maybe consider even stiffening it up a little, with some starch or something.
And other than that, I think it looks really nice! If you ever decide to go back and do anything different, be sure to post new pics ^_^