Sword Of Osman went forward from a wide gate to dispute the pace one off the fence and he wilted to fourth under Troy Harris, who replaced an overweight Opie Bosson.
"She's a super filly and she was given a super ride," Richards said.
Avantage has now won five of her six starts and this latest victory should assure her of champion juvenile honours.
Meanwhile, rising star Sherrif put up a compelling argument for a trip to Australia with an emphati win at Awapuni.
The High Chaparral three-year-old stepped out over ground for the first time in yesterday's Gr.3 Higgins Concrete Manawatu Classic (2000m) and showed staying is his game.
"Since we gelded him he's come of age. Hopefully, the sky's the limit for him," trainer Roger James' racing manager Robert Wellwood said.
Sherrif's effort will have connections giving serious consideration to the Gr.1 Queensland Derby (2400m) during the winter carnival in Brisbane.
Sherrif was among the last three in the running before a powerful closing 400m saw him too good for Gundown, also by High Chaparral, and Joe's Legacy.
- NZ Racing Desk