Let's not forget that clothes can be just a distracting as they are alluring, and by keeping her clothes very simple she's creating a clear "take-away" statement for the viewer.
The more I do this blog the more I believe that great hair and well choosen accessories can be the raison d'être for a whole look.
Remember this young lady from Savannah? I do.
Her sexy, shaggy cut created a mysteriousness about her (something I see often in France - I think French girls in particular are very good at this). Again, by keeping the fashion simple she has created a very strong and concise fashion message.
Were I a young lady I would easily spend as much on a good haircut/styling as I would on a Celine dress - after all, it's something you wear every day.
In fact, if it's a really good cut, you can also wear it in a variety of ways - not always the case with clothing.