Mills, who is ranked 28th in the world event, clocked two minutes 9.09 seconds and missed out on the gold to Canada's Melanie Schwartz on Queenstown's Coronet Peak, the Age reported.
The 45-year-old former model had won four gold medals at last year's US Adaptive Alpine Skiing National Championships in Aspen, Colorado.
She lost her leg below her knee in a road accident in 1993 and is now hoping to qualify for the 2014 Winter Paralympic Games in Sochi.
She was married to McCartney in 2002 and they divorced six years later.
--ANI (Posted on 22-08-2013)