Thanks to everybody who helped figure out where the stay went.
The material is Joanns snuggle flannel, cotton, if I'm not mistaken. I used jiffy grip as the soles so that she won't slip and hurt herself. I'm going to have to put elastic around her ankles so her feet will stay in the feet. I added four inches to the legs--two so it was long enough, and two for growth room. I also added two inches to the sleeves and two inches to the body of the shirt. The copyright on McCalls 5853 says 1944--
She picked out the fabric herself. And they've got growth room in them on purpose so they'll last through the winter. They're really suitable for a little boy, because of the fabric choice, so I figure they can be passed down to a little brother sooner or later.