This genealogy stuff is an interesting puzzle. Tee-hee--Fio almost wrote gynocology. which would also have been accurate, because births are what the whole thing is about.
Anyway, back to the subject at hand, Fiorella compared blow-ups and measurements of the three photos she has of of Kate and realized that one of them is not Kate. Prowling the annals of the family line a little, she thinks the stranger is her great-great grandmother, Anna Davis, the mother of the real Kate's husband.
And, playing around on the internet, Fio discovered there is a defunct baronetcy in the name of her mother's line. Aha! Obviously if the total royal family of England goes down, Fiorella, as the oldest child in her generation, can step in and take over.
Cheerio, old chap!