That neckline! And that pose!John Singer Sargent, Madame X (Madame Pierre Gautreau), 1884, oil on canvas, 234.95 x 109.86 cm, Manhattan: Metropolitan Museum of Art.
Sure enough, she found a sketch for John Singer Sargent's Mme. Paul Gautreau (also known as Madame X)...and there it was, minus the green teardrop earrings and Brad Pitt, but so close as to convince you that the designer must surely have had the famous dress in mind.
Here is Sargent's watercolor sketch - one of many studies he made for the oil portrait - in Joan's book, along with a picture she saw in the Seattle PI of Angelina in a pose so strikingly reminiscent of Sargent's final piece, it's as if Angelina was channeling the painting:
Here is the photo of Angelina side by side with the Sargent oil painting:
Angelina Jolie and Brad Pitt, Oscars 2009, CROP of photo from Getty Images