Billie Kay debuted in NXT on June 10, 2015, competing in a losing effort against Becky Lynch. She competed several other times as a babyface on the program, including serving as one of Eva Marie's defeated opponents. Billie became a heel (villainess) on the October 21 episode of NXT, when she adopted a more arrogant attitude in a losing effort against Asuka. As part of her villainous persona, Billie appeared at house shows with Sylvester LeFort as her manager, and competed against Divas such as Bayley, Carmella, and Gionna Daddio. On January 13, 2016, Billie returned to the NXT program and competed in a #1 Contender's Battle Royal. Billie was one of the final five competitors remaining, as she and fellow villainess Peyton Royce ganged up on Asuka during most of the match, before both women were eliminated by Asuka.
Billie Kay is portrayed as an arrogant villainess, often stating that she has "the longest legs in NXT."