Step 1:
I layed a pink paper on a white one, instead of using one paper which is colored on one side. The size is 15x30 centimeters.

Step 8:
Fold over these four lines

Step 6:
This is the backside. Fold the edges to the left.

Step 11:
Fold this edge inwards

Step 10:
Fold these two edges outwards, see arrows.

Step 9:
Fold these two edges inwards

Step 5:
Prefold both edges to the centerline and unfold the fold of step 3

Step 7:
Prefold the edges over these lines and turn the model.

Step 3:
Fold over this line

Step 2:
Fold over the purple line.

Step 4:
Prefold in half

Step 12:
Curve the model and glue / tape both ends together.

Step 13:
Open the pleats, also on the backside.

Step 14:
This is the back, fold over these two lines.

Step 15:
This is how the back should look.

Done!

Pictures: Pleated Sailor Dress for Dolls and a Dollhouse Origami Cat