I think the (medically documented) youngest mother was 9 in Africa. BUT, this story, I don't believe. It could be true, but when they start talking about when she started menstrating, puberty, etc, that kinda gets carried away and gives it away that somebody has a very creative imagination. I wouldn't believe it for an instant.
A University medical professor (in your town) could probably give some insight into what is on record. The internet creates EVERYTHING, and EVERYTHING creates the internet.

Good luck!