The Australian's time at Brisbane's Chandler Aquatic Centre was two minutes 22.96 seconds, 0.03 seconds faster than the previous mark of 2:22.99 set by China's Hui Qi in 2001 and American Amanda Beard in 2003.
"That's quite a shock," 18-year-old
"I can't begin to explain to you how much hard training we've been doing. It's hard to imagine what times are possible (in future).
"I'd like to see what I can do rested. To tell you the truth, it didn't even hurt that much.
"It was sort of one of those races where everything just happened. I just set my mind really clear, just really relaxed and just tried to hold it that way."