In September 2015, Moon signed a contract with WWE, and was assigned to their developmental territory, NXT. She made her in–ring debut at an NXT house show on October 10 in a tag team match. She wrestled as Adrien Reese or Adrienne Reese from October 2015 until June 2016. At NXT TakeOver: The End on June 8, 2016, she defeated Peyton Royce during a dark match under her new ring name, Ember Moon. After a series of introductory vignettes, Moon made her television debut at NXT TakeOver: Brooklyn II, defeating Billie Kay. Throughout the following months, Ember Moon went on a winning streak both in tag team and singles matches until losing to NXT Women's Champion Asuka at NXT TakeOver: Orlando on April 1. In May, Moon sustained a shoulder injury after being thrown out of the ring by Asuka, and could not compete in a fatal four-way match for the NXT Women's Championship at NXT TakeOver: Chicago; the match was subsequently changed to a triple threat match between Asuka, Nikki Cross, and Ruby Riot.
Moon returned on the June 21 episode of NXT and defeated Peyton Royce. On August 19 at NXT TakeOver: Brooklyn III, Moon was once again defeated by Asuka, who successfully retained the NXT Women's Championship. In August, Asuka had to vacate the NXT Women's Championship due to an injury. On November 18, Moon won the vacant NXT Women's Championship in a fatal-four way match, defeating Royce, Nikki Cross, and Kairi Sane. Asuka then made a surprise appearance and handed the championship to Moon. On the December 27 episode of NXT, Moon successfully defended her title against Sonya Deville. After the match, Moon was confronted by Kaire Sane, who was then attacked by the debuting Shayna Baszler. At NXT TakeOver: Philadelphia, Moon retained her title against Baszler despite suffering a (kayfabe) arm injury. The following night, she competed in the first women's Royal Rumble match at the 2018 Royal Rumble. She entered at #23 and was eliminated by Asuka, the eventual winner. At NXT TakeOver: New Orleans, Moon lost the NXT Women's Championship to Baszler via technical submission, in her last NXT match.
On the April 9 episode of Raw, immediately after WrestleMania 34, Moon made her official main roster debut, teaming with Raw Women's Champion Nia Jax to defeat Alexa Bliss and Mickie James. At Money in the Bank, she participated in the Money in the Bank ladder match, but failed to win the briefcase. At WWE Evolution, she wrestled in a battle royal and was the last participant eliminated by Nia Jax. At the 2019 Royal Rumble event, Moon competed in the women's Royal Rumble match, entering at number six and lasting 52 minutes before being eliminated by Alexa Bliss. During the match she suffered an injured elbow requiring surgery, keep her out of action.
She returned at WrestleMania 35 in the WrestleMania Women's Battle Royal, from which she was eliminated by Lana. During the 2019 WWE Superstar Shake-up, Moon was moved to the SmackDown brand. In June, she competed in her second Money in the Bank ladder match but was unsuccessful. Throughout June and July, Moon feuded with Mandy Rose and Sonya Deville, who bullied her. After losing singles matches to both DeVille and Rose on the June 25th and the July 2nd episodes of SmackDown, respectively, Moon teamed up with SmackDown Women's Champion, Bayley to defeat Rose and Deville on the July 16 episode, ending the feud. After the match, Bayley picked Moon as her challenger for SummerSlam, where she would go on to lose. Moon would then suffer an ankle injury, and she was not in either of the draft pools for the 2019 WWE Draft in October. She appeared on the November 19 episode of WWE Backstage as an analyst and stated she would be out of action for an indefinite period of time.
In September 2020, vignettes advertising a mysterious figure appeared on NXT on consecutive weeks. The mystery figure turned out to be Moon, who made her return at NXT TakeOver: 31. She appeared following Io Shirai's successful defense of the NXT Women's Championship against Candice LeRae, staring at the champion while also sharing a smile with her. On November 28, Ember would join Team Shotzi with Shotzi Blackheart for NXT TakeOver: WarGames. From there on, Moon would begin teaming with Blackheart and compete in the first ever women's Dusty Rhodes Tag Team Classic, where they lost to Dakota Kai and Raquel González in the finals. On the March 10, 2021 episode of NXT, Moon and Blackheart challenged Kai and González for the newly-created NXT Women's Tag Team Championship, successfully defeating them to the win the tag team titles. At NXT TakeOver: Stand and Deliver, they successfully retained the titles against The Way (Candice LeRae and Indi Hartwell). On the May 4 episode of NXT, Blackheart and Moon dropped the titles to The Way in a street fight, ending their reign at 55 days. At NXT TakeOver: In Your House, Moon challenged Raquel González for the NXT Women's Championship, but was defeated. On November 4, Moon was released from her contract, ending her six-year tenure with the company.