She bettered the previous mark of American Janet Evans, set on September 22 1988 at the Seoul Olympics, by 0.82 second.
"I was quite nervous after all that had been written in the newspapers," she was quoted by saying by sports daily L'Equipe's website. "Frankly, I didn't think I would do it."
Evans still holds the oldest record in women's swimming - the 1,500 metres freestyle record she set on March 26, 1988, in Orlando, Florida.
Also read: Justin Gatlin sets 100m world record
