During an episode of her podcast "me & dad radio," the Grammy winner, 18, revealed she became a huge fan after listening to one of Katharine's songs called "Over It."
"I think I was 12 or 13 -- and dad was playing this 40-second version," Billie began, explaining how her father discovered the ditty on Limewire. "It was the chorus -- that's all there really was. And the chorus has this beautiful melody -- one of those melodies that makes you feel something."
"I'm such a melody whore," she quipped. "God, melodies really get me. And this one really got me and got dad too."
The "Bad Guy" songstress revealed she was a huge fan of Justin Beiber as her mother, Maggie Baird, chimed in to say it reached a crescendo with the release of his music video for "As Long As You Love Me."
"I remember this one really well and the video, and Billie talking about it, and being excited it was coming out, and just crying and crying," Maggie said. "Everyone knows the whole Billie, Justin Bieber thing but this song was a big part of it."
Billie agreed, saying she "would watch the music video for this song and just sob."
"I just want to say -- we did consider taking you to therapy because you were in so much pain over Justin Bieber," Maggie quipped.