Bonneval, who was also crowned the New Zealand Bloodstock Filly of the Year at Trentham, settled toward the rear of the field before Cameron made a move 1000m from home.
"They went quickly enough early and Matt had to get rolling on her and ride her like the best stayer in the race," Forsman said.
Bonneval got to the front early in the run home and she proved too good for a game Devise in the closing 100 metres.
"I got a long way back and the speed was genuine before they buttoned it off 1200m out so I decided to get going," Cameron said.
"She's a class filly and when she got to the front she pricked her ears."
Raced by Alister Lawrence, Terry Jarvis and John Rattray, Bonneval is a sister to the group three winner Imposing Lass and a half-sister to the group three winners Full Of Spirit and Lady Cumquat.
Devise, whose half-sister Zurella finished runner-up in the Oaks five years ago, enjoyed a good run near the pace and she fought on grimly with Savvy Dreams taking third ahead of the winner's stablemate Nicoletta.
- NZ Racing Desk.