Actually, I think it's almost a guarantee that she is embarrassed and has not "moved on" to use the common phrase. Rather I suspect she is "moving" because that's what you have to do to get to the past tense of the thing.
I am in no way a feminist. I identify as a humanist. That said, there are differences in the ways the genders deal with and are dealt with by the world.
For instance. William was also naked from the waist up. Did this factor into anything at all? Are the headlines saying "William and Kate's Naked Breasts". No. Have we discussed whether William should have bared his chest? No, that would be silly, right? The female body is treated differently by society. Full stop. Undeniable, self evident truth.
So, the violation to Catherine is very sexualized and thus is tied, in ways we have not yet evolved past, so rooted are they in our evolutionary imperatives, to her sense of her place in society. It's not so much how she feels about herself, but how she knows, instinctively, that society now sees her differently. She has very deliberately presented herself in a very neutral way, in this regard. She has never once put a foot wrong in presenting a strong, feminine personality who does not need to send any overt sexual signals. What they did was sexualize her ... shifted the way the world, or some portion of it, sees her. Even if we hold her blameless, even if we sympathize with her, even if we feel protective and outraged, every one of us has a slightly altered perception of her now. Cannot. Be. Helped. It's part of the human condition we can't wish away - our worldview is like the law ... every experience builds upon the last ... we can't unring bells.
So, yes, I guess she is embarrassed. The same way you or I would be if we got photographed naked and our Moms and Dads, friends, relatives and strangers all saw the pictures. To quote my 15 year old niece, "Eeeeew."
Catherine couldn't instantly separate the intellectual condition of "I did nothing wrong" from the responsive condition of "OMG" any better than any one of us could, I would say. As proof I offer the oldest recorded piece of narrative on human nature: Adam and Eve and the Great Fig Leaf incident of '00, if that's the mythology you follow.
Or something like that. YMMV