What I have been reading here in the US, is that the Queen is making her upgrade some of her wardrobe and jewelry. William is getting more into the Family Business, and she needs to seriously upgrade her appearance a bit. I suspect that the Queen is far more informed of what we think of Kate's appearance than we thought.
It sounds like to me, she is no longer going to be able to get away with her usual attire and jewelry, especially when they go overseas in several months. Representing the Family, she is going to be in a lot more serious jewelry than in the past from what I have been reading.
I loved that necklace on her. I don't mind her leaving the back long, but if she would have just put up the front, it would have looked a whole lot more sophisticated. I am beginning to wonder if she is afraid of becoming too posh.