Dawn competed in her first match in WWE on NXT, for the NXT Women's Championship number one contendership, in a triple threat match on June 18, 2018, when Toni Storm defeated her and Killer Kelly. Dawn was defeated in the first round of the 2018 Mae Young Classic against Nicole Matthews on August 8, 2018. On August 25, 2018, she competed in the first round of the NXT UK Women's Championship Tournament, losing to Toni Storm. On July 20, 2019, she lost to Nina Samuels on NXT UK, and then beat Samuels on January 17, 2020. On September 17, 2020, Dawn competed in the first singles match on NXT UK in nearly six months, in a loss against Aoife Valkyrie. On October 15, Dawn would lose again, this time to Piper Niven. Dawn would look to improve her win/loss record on November 16, when she took on Jinny. However, Dawn was defeated by Jinny.
On December 10, Dawn would finally gain a victory over Xia Brookside when Nina Samuels caused a distraction. The following week, Dawn would get a non-title opportunity against Kay Lee Ray, in a losing effort. On February 11, 2021, Dawn would be the first opponent of newcomer to NXT UK, Meiko Satomura, where Dawn was defeated. Dawn would return to action again on March 25, successfully defeating Aleah James. On April 1, Dawn attacked the returning Emilia McKenzie, thus turning her heel in the process. Kay Lee Ray and Isla Dawn faced Satomura and Emilia McKenzie at NXT UK: Prelude on April 8, but Ray and Dawn were defeated. However, the following week, Dawn would defeat McKenzie one-on-one. On the November 25 episode of NXT UK, Isla Dawn defeated Aleah James. On the January 20, 2022 episode of NXT UK, Isla Dawn defeated Emilia McKenzie.
On the February 24, 2022 episode of NXT UK, Dawn interrupted NXT UK Women's Champion Meiko Satomura's celebration and wanted a shot at her title, then attacked Satomura and stole her flowers. She received her title match on the March 24 episode of NXT UK, but lost. After the match, Dawn stole the title. On the April 14 episode of NXT UK, Dawn returned the title to Satomura, but demanded another match under her own 'chaotic' rules. On the May 5 episode of NXT UK, Dawn got her rematch against Satomura in a "World of Darkness" match, but failed to win the title again. On the June 23 episode of NXT UK, Dawn returned and defeated Myla Grace. On the July 21 episode of NXT UK, Dawn defeated NXT 2.0's Fallon Henley. On the August 4 episode of NXT UK, Dawn fought Blair Davenport to determine the number one contender for the NXT UK Women's Championship, ending in a no contest. On the final episode of NXT UK, Dawn competed in a four-way elimination match to determine the number one contender to the NXT UK Women's Championship, which was won by Davenport.
On the November 15 episode of NXT, Dawn made her first appearance on the American brand by interfering in the Last Woman Standing match for the NXT Women's Championship, spitting black mist into Alba Fyre's face and pushing her off a ladder into the announce table, allowing Mandy Rose to retain her title. She made her in-ring debut on the December 6 episode of NXT by defeating Thea Hail. After the match, Dawn was attacked by Fyre and sprayed poison mist into a referee's face that was intended for her. Four days later at NXT Deadline, the two had a match where Dawn was victorious. On the January 3, 2023 episode of NXT, Dawn fought Fyre in an Extreme Resolution match, which she lost. On the January 13 episode of NXT Level Up, Dawn defeated Jakara Jackson. On April 1, at Stand & Deliver, Dawn and Fyre defeated Fallon Henley and Kiana James to win the NXT Women's Tag Team Championships, making them the first titles in Dawn's career.
As part of the 2023 WWE Draft, Dawn, along with teammate Fyre, was drafted to the SmackDown brand, while still the reigning NXT Women's Tag Team Champions. Fyre and Dawn made their SmackDown debuts on May 19, defeating Valentina Feroz and Yulisa Leon. On the June 9 episode of SmackDown, Fyre and Dawn was confronted by the WWE Women's Tag Team Champions Ronda Rousey and Shayna Baszler, who challenged them to a unification match, which they accepted. On the June 23 SmackDown, Fyre and Dawn lost the NXT Women's Tag Team Championships to Rousey and Baszler. Fyre and Dawn returned on the December 22 episode of SmackDown, attacking Damage Control during a "Holiday Havoc" match. Soon after, the team of Fyre and Dawn began competing under the team name of The Unholy Union.
During night one of the WWE Draft on April 26, Fyre and Dawn were drafted to the Raw brand. On June 15, at Clash at the Castle: Scotland, The Unholy Union defeated Bianca Belair and Jade Cargill for the WWE Women's Tag Team Championships in a triple threat tag team match also involving Shayna Baszler and Zoey Stark, making The Unholy Union the second female tag team to have won the WWE and NXT Women's Tag Team Championships. On July 30, Fyre and Dawn successfully defended the titles against Lash Legend and Jakara Jackson of The Meta-Four during week one of The Great American Bash.