M-M is a risk taker, and Emilio Pucci is the king of fit. I don't see anything amiss with the cut of this dress. In fact, I think it balanced her out, since she can look wide in the hip and short in the shoulder sometimes.
As for her hair, it was very retro, and I still don't see where people complain about her hair color. The roots didn't look particularly dark? And she's Scandinavian, so the tint of her hair seems natural enough for that part of the world.
Overall, this was a wonderful outing for M-M. FWIW if she's into edgier fashion choices, this is the way to go IMO.