FYI: I didn't use a pillowcase but you can. Instead, I bought some blue fabric with a cherry blossom pattern, matching thread and some pink ribbon for the top. I used a couple tutorials, here and here, and kind of melded them together to create the dress. It turned out a little smaller than I had hoped, it's only February and this is more of a spring/summer type of thing. I like the fact that it can be worn as a tunic with some leggings when she gets too tall for it. All in all it's a pretty versatile piece.
I loved how it turned out. I will definitely be making more as spring gets closer. I think I actually had her convinced that she liked it too!