I think that it is impossible for anyone to ever be completely original in the way that they look or dress, so there is really no use in labelling this person or that person as a copycat or imitator...
Why shouldn't sienna be influenced by past looks or by Kate Moss? All of the arguments of this celeb vs. that celeb get very old very quickly and frankly are a waste of time imo
I think we should try to focus on whether the look is well done and whether it works on the person who is wearing it. Not whether the same sort of thing has been done before or if they have been influenced by someone else....
I'm sure most of the posters in this thread and in other threads have styles and wardrobes that are influences by what we see on the celebs... it's a great way to get ideas and then see how you can work it into your own life...