Joining them in Sunday's Final are Brazil, Germany, Switzerland, Belgium, United States, Ireland and France.
These Pan American Games in Santiago are critically important to qualify Canadian teams for the Paris Olympics next year.
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.
Opglabbeek, BEL hosted the FEI Jumping Nations Cup Youth Final, the culmination of 10 legs across Europe since March.
The 2023 Championship title has become a three-man race as the LGCT galloped into historic Circus Maximus in Rome.
Competition wrapped up at the Ottawa National tournament, the final show jumping event of the 2023 season at Wesley Clover Parks.
A unique 16-acre equestrian oasis close to an urban centre, SRC has been providing members with facilities and events for decades.
Foster rode two spectacular rounds and a jump-off in the $3 million class aboard Figor on a day which saw four Canadians in the top 12.