I have put together a tutorial on making a Pillow Case Dress for any doll.
First find the largest measurement between under the dolls arm and above the ankles. On Arielle it was the hips/stomach;add one inch. Also measure from the shoulder to where you want the dress to come to; add two inches.
After cutting out you rectangle fold in half.
Then fold the fabric ends into the middle.
Measure from the top of the doll’s shoulder to under the shoulder.
Now from shoulder to neck.
Use the shoulder measurement on the long side/fold and the shoulder/neck on the top/short side.
After cutting out the arm holes on both sides this is what it should look like.
Now hem the arm holes and the bottom.
Sew the sides of the fabric together to make a tube.
Now make a tube to put the ribbon in on the top.
Now your doll has a new dress!