And the winner is:
Stylish Fabric with their Teal 52" pleated poly cotton voile, upper left corner. As you can see, the Crushed Taffeta in Teal by Big Z Fabric (upper right) is too blue, and too shiny. The selection by Mood Fabric has a good Accordian Pleated Teal Chiffon, but I feel it is too thin and the pleats too big for Ophelia's dress.
More about the dress, as well. The designer for Ophelia's costumes is Massimo Cantini Parrini, an Italian "Fashion Archaeologist". You can read an article Vogue did about him: Vogue on Ophelia's Costumer.
He was drawn to Waterhouse and other Pre- Raphaelite artist, jewel tones and inspired by the famous Delphos style dresses by Mariano Fortuny. It was so ironic when I read that in the article, I went and dug out one of my MANY costume resource books and thumped it open to the page on the Delphos dress. Here is an example of one such Fortuny Delphos:
These dresses are gorgeous, I recommend checking out another Vogue article on Fortuny: From Invention to Eternity You can see how the pleated underdress and side laced overdress inspired Parrini!
There was one other possibility for my rendition of Ophelia's dress, and that was an Accordian Pleated Teal velvet. I felt this would be too heavy and I was unable to acquire a swatch beforehand. So I guess cotton voile it is!