Choo made her debut in WWE when she entered the 2018 Mae Young Classic under the name Karen Q. During the first round, she lost to Xia Li. She later faced off against Rachael Evers, whom she lost to in a match during the Mae Young Classic 2018 tapings. In July 2019, Karen suffered a fractured lateral malleolus, where she spent the next two years rehabilitating, undergoing two surgeries. In December 2020, she was reintroduced on NXT as Mei Ying, the leader of the stable Tian Sha alongside Xia Li and Boa. She returned to the ring in August 2021. In November 2021, the Mei Ying character was dropped and she was again repackaged, this time as Wendy Choo. In March 2022, Choo and Dakota Kai competed in the Dusty Rhodes Tag Team Classic, losing to Io Shirai and Kay Lee Ray in the finals. In June 2022, at In Your House, Choo unsuccessfully challenged Mandy Rose for the NXT Women's Championship. Choo went on to feud with Tiffany Stratton, defeating her in a Lights Out match in August 2022. In February 2023, Choo suffered an unspecified injury; she was written off television to allow her to recuperate via an angle that saw her attacked in a parking lot. Choo returned from injury in April 2024, facing Wren Sinclair on NXT Level Up. The following month, she returned to WWE television under a new, more aggressive persona. In July 2024, Choo formed a short-lived alliance with Tatum Paxley, which ended the following month when Choo turned on Paxley during The Great American Bash after Paxley failed to defeat NXT Women's North American Champion Kelani Jordan for the title.
In September 2024, Choo formed an alliance with the debuting Rosemary, attacking Jordynne Grace during her open challenge.