"I guess it's about emotions and trying to channel them in to something productive. I think the writing really helps if you're having a bit of a weird time, and don't feel like you can talk to anyone else about things, writing things down makes it better. I think originally I started writing because I didn't feel like I fit in anywhere."
In the end it was a seemingly insignificant decision to follow a friend to music college that lead her down the path to forming Daughter, the band she brings to Laneway on Monday and which first formed in London in 2010.
"He was going, and I was kind of interested in this new course they were setting up, a songwriting course, and also because I didn't really know what to do with myself at that time, at 19, so I thought, why not?
"And then I met Igor Haefeli [guitarist] through that course, and Remi Aguilella [drummer], and we started playing together. I was actually thinking the other day, how if I hadn't followed my friend to that course, I wouldn't be playing a gig in Hamburg, or New Zealand."
The band has moved on from fleshing out Tonra's songs, to working collaboratively , though Tonra finds her lyric-writing process has similarities.
"It's still a similar mental process for me with the lyrics, they tend to come all at once, and though they might be connected to what's happening in my life, they often come from nowhere, they just sort of arrive when I'm in the right frame of mind. The 'dark room by myself' effect is always a good one. And I've noticed I seem to be quite interested in writing about death. Not in a maudlin way, just because I'm interested in what happens."
Their music is hard to categorise - they've had all sorts of hyphenated descriptions, including "f***ed up folk musicians', which Tonra isn't surprised about given her family background.
"I'm half Irish, and I was brought up listening to a lot of traditional Irish folk tunes, like my grandfather would sing them, so I think there's definitely something in that, what I grew up with. So I'm not surprised that that has seeped into the music, even if it's to do with the way songs are structured, or the type of melodies I like. I think everyone can't help be influenced by their life of listening, even if it's not conscious. My dad also loved Neil Young and Bob Dylan, and I loved Jeff Buckley pretty intensely as a teenager."
Mostly they just write whatever comes naturally, and they're happy not to have any definitive genre label.
Though the band's 2013 debut album If You Leave after signing to indie giant 4AD, the album winning praise for its ethereral sound and melancholic mood.
"We don't mind at all if people call us f***ed up folk, or shoe-gaze, or alt-rock, or ambient, or whatever, we've been called a lot of things, and it's quite nice to feel like we're not being defined as one thing - that means we can go anywhere really."
So what might fans expect to hear from them on stage at Laneway? Well their many-layered songs are given a boost by having a fourth live band member, and Tonra thinks they're naturally more lively.
"We didn't necessarily want to recreate the album dead-on, sound for sound, but we want to achieve the same vibe. People have said we're a bit more aggressive sounding on stage, a bit harder, maybe a even a bit more dynamic.
"We're still a bit awkward though," she says with a laugh. "I don't have any particularly great jokes or dance moves sadly, but I think we're enjoying it now - even if we do look at our own feet sometimes."
Who: British trio Daughter
Where and when: Performing on the Hey Seuss stage at Laneway at 2.25pm
Listen to: If You Leave (2013)