This doesn’t look like it’s an intentional showing. Bad choice of underwear for someone being followed by paparazzi with high quality camera lenses, true, but she probably didn’t have to worry about such things before since any pictures taken would have been illegal to print. (I assume. England seems to have some 16+ nudity allowances according to a friend.) Her undergarments might become a bit more sedate now.
Edit: I’ll also just note that if I’d thought it was a voyeuristic shot of her, I wouldn’t have looked. From the OP I’d thought they were posed, and approved by the target, photos.