The dress Nellie is wearing is from the Enchanteddesigner on Etsy. See my previous post. I like the diaphanous material. This is best rendition I've seen so far. It so much prettier in person.
I found a comprehensive description of the dress from Rebel's Haven, who is attempting to recreate the movie dress.She does great research right down to the buttons, which were apparently procured by the movie costumer from Huscco Buttons.