Her best result up until now is winning the 420 World Championships in 2007.
Today's win puts New Zealand's medal count to four and is the country's first win in the category since 1984.
Aly Raisman, the American Jewish gymnast, has won two golds at this year's Games.
Speaking after her win, Ms Aleh said it was "pretty awesome" to be flying home with a gold medal.
