Irwin began competing at the FEI Nations Cup in 2015. On March 15, she and Fancy That achieved a first-place finish in Freestyle at the Adequan Global Dressage Festival in Wellington, Florida, with a score of 74.375%.
2016 FEI Nations Cup
In February 2016 at the ADGD, Irwin, on top of Laurencio, won first in the Intermediaire I twice with 76.842% and 76.579% respectively. She also placed sixth in Prix St. Georges with 68.289%. Later in March at the AGDF, Irwin scored 70.307% in the Prix St. Georges and 70.368% in the Intermediaire I. From May 20 to 22, Irwin and Laurencio competed at the Ottawa Dressage Festival and placed first in all three of her events. She scored 74.333%, 73.509%, and 71.404% in Freestyle, Intermediate I, and Prix St. Georges respectively. She completed the same feat from June 17 to 18 in Cedar Valley, York Region, Ontario. Irwin placed first in Intermediate I with 74.605%, Freestyle with 79.208%, and Prix St. Georges with 71.974%. From September 30 to October 2, Irwin completed yet another sweep of the events she participated in, in Devon, Pennsylvania. On Laurencio, she scored 71.009% in the Prix St. Georges, 73.579% in the Intermediate I, and 77.175% in the Freestyle, placing first in all three events.
2017 FEI Nations Cup
At the AGDF on February 23 and 25, Irwin placed third in the Prix St. Georges and Intermediate I events with scores of 69.781% and 73.860% respectively. On February 26, during her Freestyle performance, a power outage resulted in a stoppage of music, and she was forced to start over. On her second attempt, she achieved a 2017 world record small tour score, achieving a score of 78.708%. Later, in March at the AGDF, Irwin placed first in the Intermediate I with 73.237%, Freestyle with 76.500%, and Prix St. Georges with 74.026%.
2018 FEI Nations Cup
At the AGDF, Irwin made her debut in Grand Prix events; she placed fifth in Grand Prix freestyle with a score of 68.700%. On May 19, Irwin competed in Grand Prix freestyle at the Ottawa Dressage Festival, where she won silver with a score of 67.700%, 2.75 percentage points behind Jill Irving.
2019 FEI Nations Cup
In 2019, Irwin returned to small tour competition, as opposed to Grand Prix, in attempt to qualify for the 2019 Pan American Games. Prior to the AGDF in Wellington on February 20, 2019, Irwin injured her left hand as a result of a kick by a horse. On February 21, 2019, her husband, Jaimey, took over for her on Laurencio, placing first with a score of 71.324. On March 5, 2019, Equestrian Canada announced that Irwin would be on the Canadian dressage team competing at the AGDF, along with Jill Irving, Lindsay Kellock, and Belinda Trussell. Canada won silver at the event with a combined score of 433.685, 4.008 behind the United States. Irwin achieved a personal best with a score of 74.912%, then followed up with 73.588% on her second attempt. Later in March, Irwin won all three small tour events at the AGDF. She scored 74.460% to win the gold medal in Freestyle, 73.588% to win Intermediate I, and 74.912% to win Prix St. Georges.
2019 Pan American Games
It was announced on July 19 by the Canadian Olympic Committee and Equestrian Canada that Irwin would be a part of the Canadian team participating in the team dressage event at the 2019 Pan American Games in Lima, Peru. On July 29, she competed on top of Laurencio, alongside teammates Jill Irving, Lindsay Kellock, and Naima Moreira Laliberté the team won gold with a score of 440.111, 2.2 points ahead of the American team's 437.791. Their performance qualified Canada for the team dressage event at the 2020 Summer Olympics in Tokyo, Japan. On July 31, in the individual event, she placed second with a score of 77.780%, 1.2 percentage points behind first place American, Sarah Lockman, who scored 78.980%.