But while the Brisbane result ticked another box in her quest to fulfil the Para Olympic selection criteria, another crucial one still remains unchecked.
"While I have fulfilled all requirements as set down the by the FEI (International Equestrian Federation) of three scores with International judges over 62 per cent the New Zealand criteria is tougher," she said.
"I have to achieve four international scores of 70 per cent, and compete at a CPEDI3. I am one score short at this stage."
With just one more qualifying CPEDI show, held near Melbourne in November, her hopes rested on a qualifying event being organised in New Zealand next year.
"Financially that (Melbourne) is not an option for me," she said.
"There is a slim possibility Equestrian Sport New Zealand may hold a qualifying event in NZ next year. If they do, it would be cutting it fine to tender an entry for Tokyo, but I have to work on the belief it will happen."
Duncan, who is currently ranked 45th Grade IV Para Equestrian in the world, was feeling positive about the future, even if she missed out on Tokyo.
"If I don't get to Tokyo, there's always Paris in a few years, "she said.
"Either way, I'm giving this my very best shot. I am hugely grateful to everyone who has been so supportive on my journey."
The journey hasn't been a smooth one. Last year Duncan won the Grade IV Para Horse of the Year title riding Don Ivanno, but tragically the horse was euthanised just months later after a paddock accident.
Duncan was given another horse, Northern Ivanthus, by her mother Frankie Webb and reclaimed the title this year, giving the horse qualifying scores towards Tokyo.
But fate reared its ugly head again, and three weeks later the horse suffered colic, requiring life saving surgery at Massey Equine Hospital. He was due to return to work this month.
"I had to choose between abandoning my quest for Tokyo, or try to qualify Spirit," she said.
Spirit has been runner-up to his stable mates at Horse of the Year on both occasions and had captured the 2019 Dressage NZ National Grade IV title.
"He is my soul mate. I have every confidence he can step up to the mark."
Spirit had to fly from Auckland to Sydney, and then make an 11-hour road trip to Queensland State Equestrian Centre at Caboolture, with only three days to recover before competition.
Temperatures were in the mid 20s every day but facilities at the Centre were second to none, with both warm-up and competition arenas being indoors.
Judges from Australia, New Zealand and USA officiated at the competition. Duncan was the only rider to fly the New Zealand flag, competing against Australian riders already named on the Australian short list for Tokyo.
Duncan drew number one on the first day for the FEI Grade IV Teams Test. Due to a technical issue, she had to ride her tests from memory as opposed to having them commanded as was usual for her.
"Mum is an ESNZ coach. She helped me warm up, she kept me focused," she said.
"I wanted to make sure I remembered the test. A course error would be very costly."
Error free, Duncan emerged the winner on a score of 65.33 per cent, narrowly ahead of Australian Kaye Hannan on Bradford Park Wexford scoring 64.708 per cent and Sarah Sherwood, Australia, on Janevelyn Tsunami 56.917 per cent.
Riding the FEI Grade IV Individual test on day two, Duncan had a more convincing win with all three judges placing her first, achieving an over all score of 66.423 per cent, American judge Kristi Wysocki giving a score of 68.049 per cent
The second placed rider, K. Hannan, scored 63.740 per cent. Duncan was pleased with her score which under FEI rules was a Para Olympic qualifying score, but not quite the 70 per cent required by Equestrian Sport New Zealand.
The final competition, the Grade IV Musical Freestyle, was not included for Paralympic qualification. Duncan scored a trifecta winning on 70.317 per cent, all judges giving over 70% and first place, well ahead of runner up Hannan on 66.492 per cent.
Duncan had some unexpected support in Brisbane. Levin veterinarian Rob Bloomfield and his wife Carol arrived in Caboolture at the prize giving on day one of the competition and stayed to support her throughout the event.
And the breeder of Wolkenstein BC, Chris Beach, and her husband Tony, were also in support having travelled from Auckland to Brisbane.
Duncan thanked Horowhenua Dressage Group for their grant towards horse feed and travel expenses, while Olympic Dressage Coach Andrea Raves donated a training session.
