Yet teenage girls were packed tight at the front of the stage, many of them visibly emotional as they hung off every word sung by the diminutive 20-year-old.

There is something beautifully sweet and innocent at the heart of Mallrat's electro indie-pop and it's caught fire.

The Brisbane artist's 2018 single Groceries about the classic teenage issue of having an unrequited crush has clocked up 33.5 million streams on Spotify.

American audiences are also beginning to take notice. When Weekender catches up with Shaw she is unpacking at her Los Angeles home after returning from a sold-out gig in Minneapolis.

"I don't really know what to think about it," Shaw says of her music's impact on the audience.

"I'm just grateful I can make music that means something to people.

"I'm not doing music to be a cool musician, I just make songs to help people or let them have a little world to hide in when they don't like what's really happening.

"That's what music is for me."

Shaw spent the majority her childhood in Brisbane, but briefly went to primary school in Maitland where she remembers heading into Nobby's Beach with her family to see where "the Pasha Bulker was washed up."

In 2016 Shaw, then 17, released her first single Sunglasses under the name Mallrat, where she combined pop vocals and rapping over heavy programmed beats.

A year later Triple J and English magazine NME were firmly behind Mallrat's singles Better and UFO, where she ventured away from her previous rap stylings in favour of melodic indie pop.

Both singles would appear on Mallrat's second EP In The Sky, released last year.

"When I started I was just finding beats on [music sharing website] Soundcloud or people were sending me beats they'd made and I'd go to my friends studio after school, or when I graduated I'd catch the train from work in the city and record," she says.

"Now I've learnt more about production and I'm really involved in it. I'm not really using Soundcloud anymore, it's more producing it myself or being in the room with the producer I like or a guitarist I like and building it all together and then doing the vocals."

There's a nostalgic and child-like quality to Mallrat, which explains much of her appeal. This is true of her emotional new single Charlie, named after her labrador.

It's the lead track off her forthcoming third EP, Driving Music, out on September 6.

"I feel like a little kid in a lot of ways," Shaw says. "I love hanging out with little kids. I did babysitting for ages and it was my favourite job and I did tutoring when I was in high school and after I graduated.

"I'm just so inspired by children and kids movies and books. Just how imaginative, colourful and pure they are. I try to always keep that."

Charlie isn't all about comforting childhood nostalgia. The track also addresses her parents' relationship issues when she sings, "Daddy worked out west and he worked so hard / My mum she smells like cigarettes and they broke each other's heart."

Did her parents approve of her opening up about their problems to her rapidly-growing fan base?

"I showed my Dad and he liked it, but I was really scared," Shaw says. "I got a message from my Mum, which I haven't opened yet, but it started with, 'Charlie is beautiful', so she can't be too upset."

Mallrat performs at Grapevine Gathering at Roche Estate on November 30 alongside Two Door Cinema Club, Flight Facilities, Jack River and more.