I just wanted to start by saying out of all of Kate’s “Marilyn’s moments” (I hate this term), this wasn’t the worst. It was an unfortunate day that happened to be windy, and she was only outside for a few moments to meet the dignitaries and then she was inside, so she probably didn’t put too much thought into the wind. In fact I thought the skirt was a nice length overall, and it wasn’t super flimsy (like the Topshop black and white polka dot). I also liked the whole outfit overall.
With that, I do think she should be more careful to avoid the “Marilyn’s moments”, especially when she attending events as the Duchess of Cambridge. She isn't an ordinary person (like me) or a celebrity (although she is technically a celebrity, she is first a royal). I could get away with wearing a skirt and having it caught by the wind for a millisecond because I don't have hundreds of photographers taking my picture at that moment. I might be embarrassed, especially if a passerby got a view of something, and I would probably end up holding down my skirt in case of another gush of wind (although I would probably not wear a skirt if it was that windy).
But as a royal, she can't be "flashing" the public and photographers (I know nothing was exposed but I don't think seeing a lot of upper tight is appropriate at these event). She also can’t be holding down her skirt because it would be awkward to do while shaking hands with dignitaries and being presented flowers. In fact when she was at the airport in Calgary, she supposedly committed “bad etiquette” by not putting her cowboy hat on because she was unable to because she was too busy holding down her dress and hair.
I think she could consider a few things in order to avoid these moments. She could wear more opaque black tights, instead of the sheer black tights. I have always found it your tights are opaque you can get away with shorter skirts because you can’t really see skin. She could start wearing more sheath dresses and skirts, and this might be the better suggestion for getting on airplanes (she didn’t have any wind issues when she was leaving for Canada or when she arrived in Ottawa because her dresses were more sheath and form-fitting). Or she could start wearing clothes that aren’t as flimsy, but she might have to move away from the high street clothes, and get more bespoken or designer clothes.
I also wanted to add that I loved her hair. I like having my hair down, but it isn’t professional to have your hair in your face and having to continuously push it back. And like me she tends to touch her hair a lot (I do it when I am nervous) so pulling it back prevents that.