The New Zealand mare - ridden by James McDonald - chased down the short-priced favourite in the home straight to win by four lengths.
It is the first Melbourne Cup victory for trainer Chris Waller.
"I love her to bits. She's been so good to me," McDonald told local network Channel 10 after the race.
"They can safely say she's a champion now.
"I never thought I would ever win one, you know. I always dreamed of winning one, but, it's so hard to win."
