Yeah I don't get including henna tattoos in the article (which was the case of the three British royals included).
As for the tattoos, what is good for the goose is good for the gander. I don't see what is wrong with female royals having them when male royals have them. As long as they are tasteful, not offensive symbols or such, nothing wrong with them. They are art work.
If that is a tattoo and not just the trim of her suit, then that is a great example. Something almost never seen in public, not going to offend any ultra conservatives shocked by a woman with ink, at an event.