The 16-year-old made the top six in the final "jump off" phase where she received the highest marks to eke out a victory.
For her stallion Clockwise of Greenhill Z it was business as usual despite a tack malfunction in the CSI3* Grand Prix.
Kyle King and 'Odie' won the Wednesday opener and Jim Ifko topped the leaderboard on Thursday with 'Monty' over Joey Rycroft's courses.
Matt Sampson shines in the CSI3* ATCO Cup Grand Prix; Tiffany Foster continues her winning ways at Thunderbird Show Park.
Fresh from Europe, Sampson takes the Challenge with Curraghgraigue Obos Flight; Chernoff is MarBill Hill U25 champion and Betker bests Derby.
Highlights from Thursday's 1.40m Challenge, MarBill Hill U25 and Canadian Hunter Derby at Thunderbird Show Park.
The Canadian rode the speedy 17-year-old to edge Robert Blanchette (IRL); her operation is now based down the road in Langley at a new farm.
The Tbird Dressage Show in Langley, BC, featured some longtime partnerships and personal bests presented to FEI 5* judge Stephen Clarke.
Tbird in Langley, BC, was the scene of CDI 3*/1* action all weekend, with Jennifer Williams and Joppe K topping the grand prix leaderboards.
The pair finished just a half-point ahead of runners-up Ashley Arnold and Light My Fire, with Sloane Betker and Crack third.