She said: “Finneas became obsessed with music!” while Billie had been exploring her talents for as long as she could.
She continued: “Billie never ever stopped singing – I mean it was insane.
“She sang practically before she talked. She sang everything, everywhere!”
Maggie revealed: “The depression was the hardest part of all this.
“We checked in with her all the time: ‘Do you still want to do this, do you want this?’
“She loved doing the shows. That’s what kept her going.”
The young star also opened up on the personal struggles she dealt with during this time.
Billie said: “I was actually clinically depressed – that was the beginning of it. But then on top of it all was the fame that I didn’t want at the time.
“It was the unability to go out places and it was so torturous, because all I wanted to do was go hang out with my friends.” (sic)
Billie previously revealed how this dark period of her life, and a collection of reoccurring nightmares, inspired the creation of her debut album, When We All Fall Asleep, Where Do We Go?
The album was released on March 29, 2019 and won her Album of the Year and Best Pop Vocal Album at the 2020 Grammys.
Speaking to Zane Lowe about her work, the youngster explained: “The album is basically what happens when you fall asleep.”
Billie continued: “For me, every song in the album… there is sleep paralysis. There’s night terrors, nightmares, lucid dreams.
“Sleep and not sleep have always been a big part of my life. I’ve always had really, really bad night terrors.
“I’ve had sleep paralysis five times. All my dreams are lucid so I control them. And I know that I’m dreaming when I’m dreaming so… I don’t even know.”
She added she can sometimes see the future in her dreams, saying: “Sometimes I’ll have dreams where the thing that was in my dream will happen the next day. It’s so weird. It’s so weird.”