She just needs some shower curtain weights sewn into the hem of her dresses.
Yes, that’s what they did to Diana’s when she would wear those full skirts. I think that’s why she started wearing the more tailored straight skirts; harder to blow up. I suspect there will be some wardrobe adjustments once she gets home.
I had the same thing happen to me with full skirts: once in front of church after it let out, and once in front of my office building in front of a co-worker (male). My blow-ups happened in the front, though. Was wearing a slip but it followed the skirt. At least I was wearing knickers!!