Acetone will remove/damage the painted areas. I have not cleaned a design a pony, but I do know acetone free polish remover is gentle on the eyes and symbols of g1 ponies so might be worth a try for Fluttershy.
If you can get a magic eraser it may help but this is a product that care has to be taken around painted areas you want to keep.
I do wonder if the pinky pink color is highlighter marker? That seems to never come off completely, so far in my experience.