Speaking to Entertainment Tonight in 2019, the star was asked if she had any way of preparing herself to perform.
She replied: “I did, I used to… The first tour I actually had a song I would warm up with, which was Sabrina Claudio!”
Sabrina is a fellow young American singer from Miami, Florida.
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Billie revealed: “It was… I think it was Unravel Me, or Belong To You. I don’t know. It was always Sabrina Claudio, though.
She added: “Now I just do vocal warm-ups!”
The star has spent a lot of time with Sabrina, including attending parties together.
Sabrina has also worked with rapper Khalid, who is one of the only artists Billie has released a song with in the past.
The Bad Guy Singer mostly works with her brother, Finneas O’Connell, who is her partner, producer and best friend.
The pair have been inseparable for their whole lives and Finneas recently spoke up about “protecting” his sister while being in the industry.
“But I always think of it, because of the amount of people we meet. I’m always trying to help facilitate the safest environment for her.”
He added: “She’s 19 now, but over the past couple of years, she was very young. And so I’ve wanted to be as protective as I can. I never wasn’t in a room with her when we wrote with other people in the first couple of years.
“Part of that was the feeling: ‘I want to keep this kid safe.’ Not to be overbearing, but just a witness. Make sure that nobody is being a creep.”