Nicoll started competing in athletics for the Birchfield Harriers at the age of 14.[2] She was not selected in the Welsh squads for the 2014 or 2018 Commonwealth Games; she only reached the B standard for the 2018 Games.[3]
In 2020, Nicoll took up bobsleigh after being approached on Instagram by Mica McNeill, who had seen videos on social media of Nicoll exercising.[5][12] She spent most of the 2020–21 season in training,[12] and lost almost 20 kilograms (3.1 st; 44 lb) of body weight in order to compete.[5]
At the 2021–22 Bobsleigh World Cup, Nicoll competed in some events with McNeill, who also competed in events alongside Mica Moore and Montell Douglas. Nicoll, Moore and Douglas were all attempting to earn a place with McNeill for the 2-woman event at the 2022 Winter Olympics.[5] In January 2022, Nicoll and McNeill finished second in the World Cup event in Sigulda, Latvia.[13][14] It was the first time that a British woman had won a Bobsleigh World Cup medal for 13 years, and it was Nicoll's second World Cup event.[13] That month, McNeill and Douglas were confirmed as Britain's selections for the Olympics;[15] Nicoll travelled to the Games as a reserve.[14] Two weeks after the Olympics, she attended a bobsleigh driving school in Lake Placid, New York, US.[2] In the 2022–23 season, Nicoll started working as a pilot, in the monobob event.[16]
At the 2023–24 IBSF Bobsleigh European Cup in St. Moritz, Nicoll and Kya Placide won the 2-women bobsleigh event, and Nicoll came second in the monobob event.[17]