I remember seeing this article awhile back.
Really made me realize that sometimes simple, trivial things that everyone takes as fact really cannot be trusted.
The notion that Coco the gorilla could do sign language was another one that stuck with me.
Anyways, I think the best evidence 'against' Jeanne is that no other super-old person simply looked (both outwardly and physiologically) like someone 20 years thier junior. All the medical evidence points to her not actually being the age she claimed she was.
I'm of the opinion the 2nd place woman is also not legitimate. She probably just lied about her age so she could marry and then lived incredibly long.
https://en.m.wikipedia.org/wiki/Sarah_Knauss