This one was too cute to pass up, despite the fact that it was thin.
This problem is easily remedied by adding a liner to the pillowcase before sewing the dress together. Allow me to demonstrate:
First, cut off the closed end of your pillowcase. Just a little bit.
Find a solid color pillowcase to be your lining. Make sure it is about the width of your decorative pillowcase. This one looks good.
Put the lining inside the decorative pillowcase. I like the lining to be 1/2 to 1 inch shorter than the outside layer so it doesn't show. Line up the bottoms how you want them.
The top part of the lining pillowcase will likely stick out the top of the decorative pillowcase. That's ok, just straighten it out so there are no wrinkles, and then double check that your bottom length of the liner is still where you want it.
Measure how long to cut the pillowcase according to your pattern. Measure from the bottom (open end) of the decorative pillowcase up, and cut across, cutting through both pillowcases.
From here on out you will treat your two pillowcases as one. Trace your armhole curves and cut out through both layers. At this point you can baste the layers together along the armhole curves to help keep it from moving on you, or you can just pin it.
Continue as your pattern directs. As you sew, just remember to treat your two layers as one. There are a ton of pillowcase dress tutorials out there so I won't go into details on assembling the dress. Unless you want me to. Comment if you want more info and I'll be happy to oblige :-)
Ta-da! It's done!
See the lining?
I was going to sell this one, but after making it I discovered a small hole in the back of the outer layer. Oh well, another one for the little gal's closet!