I read somewhere (and do not remember where it was), that the reason for rejecting the Dassier's work was that the dress shown was TOO HUMBLE, and in the Empress's opinion improper for a Russian 'барыня' (noble woman) to wear. If the dress shown were more imposing or better decorated, she might have approved the portrait. I do not know if this is just an anecdote or a true story, but I can imagine saying that would have been very typical of her based on her known habits and the life style.