As I said, the headline is correct. The text of the story is flatly wrong. There are undoubtedly people born in 1900 who are alive now, and they, not she, are the last people born in the Nineteenth Century.
I see in your future a job personally monitoring urine tests.
There are two women still alive who were born in the year 1900, one in Jamaica, one in Japan. https://en.wikipedia.org/wiki/Oldest_people#Verified_oldest_living_people
There is no controlling legal authority to say otherwise. Did some King, President or Pope say it had to be the way you are saying it has to be? There’s no law or rule or regulation saying how it has to be.
It’s simply social convention and most people don’t see it your way. How you say it is supposed to be is just your opinion, nothing more.