Copy or Inspiration?

When I came across this Liliane Romi white evening gown in a magazine from 1987, my immediate thought was, "I've seen that dress before." And I knew exactly where. The image at the left, by George Hoyningen-Huene was featured on my blog back in February of 2009. He photographed the white gown for Bergdorf Goodman in 1940.

My question is, where do you draw the line between a design being a copy or simply an inspiration? Romi had to have been staring right at this Hoyningen-Huene image when she designed these gowns in 1987. And, while they're not line for line copies, they surely are close. I wouldn't call her work original.....

....would you?