In the second picture, I notice her gorgeous colouring and hair. I see her face. In the second I see a dress.
I agree with you, Single, but I think it's a styling error. The dress makes an unmistakable statement about its era and idiom. Doing hair and shoes in keeping is what made it look fancy-dress-like: she's letting the dress wear her. Also, that print would look better on a black woman than someone as white as she is.
I will have to bow to everyone else's experience on Cos! I did an image search, but 99% of the real people looked just as droopy as the catalogue pictures 
The other 1% looked fantastic, though. Perhaps they were the Cos fans on this thread!