18-year-old Megan Bülow never expected her anti-romance anthem, Not A Love Song, to catapult her into the spotlight before she’d even finished high school. In fact, she very nearly didn’t release it at all.

bülow – who goes by her surname “because I wanted to keep it totally gender neutral” – arrived at a writing session two years ago armed with a chorus she’d recorded on her phone’s voice notes. “But it was just me and the producer who were really vibing to it,” she recalls, so the song got shelved. It wasn’t until a year later, when she and that same producer stumbled across the demo again, that they recognised its magic. “We were like, ‘What the hell, why didn’t we do anything with this?’ We ended up finishing it that day.”

The resulting song – a flirty, cutting kiss-off to a guy who’s got too attached – went viral. As more and more fans were drawn to its playful gender role reversal, it racked up nearly 20 million streams on Spotify. It reached No.1 on the Hype Machine Chart, No.11 on the Global Spotify Viral Charts, and got bülow signed to Republic Records in the US, and Polydor in the UK. She had no idea, when she was discovered by independent Canadian label Wax Records at a summer camp a few years earlier, that this is where she’d end up. “I think we expected it to be a way longer process,” she says. “Nobody expected so many people to hear that song, it was crazy.”

Not that she ever saw any other future for herself. During an unusually nomadic childhood – she lived in Germany for eight years, England for six, Texas for two and now lives in Holland – it was music that anchored bülow. “Moving around, I didn’t always deal with it very well. Having to start over is definitely difficult, but through the difficult times of not fitting in or missing home, I was able to express all the nervousness, excitement, anger and fear that I had built up, through my music.” She wrote her first song at the age of eight, inspired by her “badass” hero Avril Lavigne. By eleven, having discovered the guitar thanks to Ed Sheeran, she was busking – “I’m pretty sure illegally” – all over London. “I just showed up one day with all this gear, and my parents were like, ‘Where are you?’ I was like, ‘I’m in Kingston, busking!’”

Elsewhere, she channels the existential angst of youth. On SAD AND BORED, which features a guest verse from one of her favourite rappers, Duckwrth, she lists the ways she tries to keep herself busy. “I never let myself get to the point of boredom, so the song is kind of ironic,” she says. “To me, a day of doing absolutely nothing feels like an eternity of missed opportunities, where I could have become better.” But it is another line on Honor Roll that exposes her deepest fear. “It’s just that I don’t wanna get older,” she sings, “I don’t wanna die.”

Death, she says, “has been something that, since I was very young, I was very, very scared about. It was just the sadness of the fact that everyone’s gonna die.” Still, she tries to look on the bright side. “Before death, life is all about having something to hold onto, and be remembered by. That’s what’s so cool about music; it’s something that’ll always be there, for the next generations to hear. That’s what’s so powerful about it.”