Before she made her new album, Megan Washington had to ask herself some big questions. The most important of which was: what happens to the music if you’re happy?

The Australian singer-songwriter’s last two records were surrounded, in one way or another, by personal turmoil.

Her debut, I Believe You Liar, was a chart hit that earned its maker both critical acclaim and multiple Aria awards. But touring the album brought about a period of darkness in Washington’s life that included illness, the end of a relationship, a lot of partying and not a lot of looking after herself. Her follow-up, 2014’s There There, was written in the wake of a break-up and saw Washington very candidly grapple with, as she put it at the time, “being engaged and then unengaged”.

In the six years since, Washington’s life changed “in a pretty significant way”: she left her 20s behind, married film-maker Nick Waterman and had a child. She’s been working on projects outside of music – voicing a character on the ABC children’s show Bluey and making a “comedy musical podcast” called Crossbread – and things have been, well, pleasant. Which has forced her to take a different approach to songwriting.

“I used to think that I had to method act my music. I wanted it to be chaotic and outrageous and yet also full of longing and pathos and whatever, and I thought I had to live a life where all that was true,” she says, speaking to the Guardian from her Brisbane home. “And then Nick and I got married.”

“The big problem with having a happy ending is, what the hell do you write songs about? Like, if I’m no longer the victim of my relationships, and all my music was just me processing the chaos of my relationships, what happens when you fall in love and that’s it? That was a huge thing that I had to include in my process of making this album.”

That new album, Batflowers, certainly feels like the work of a happy person. It’s warm, hopeful pop music, which gets big and fun in moments like lead single Dark Parts – but is more often comforting and tender (Achilles Heart, Kiss Me Like We’re Gonna Die).

Washington says she wanted parts of it to serve as “audio graffiti” – the musical version of finding “you are beautiful” or “dump him” scrawled on the back of a pub bathroom door. She still wrote about her life on the record, but with a focus on telling stories in a way that was a little blurrier and could have multiple interpretations. And she selectively mined her earlier years for material, because “past grievances are worth writing about, don’t you think?”

The exuberance of Washington’s music is there in conversation, too. She’s passionate: her voice breaks with emotion when she talks about how “sometimes it’s really hard to be an artist in this world, especially when the government of the country that you live in is so disconnected from a place of love.”

But there’s always humour laced into her Big Statements, like when she quotes Nietzsche to make a point – but only after a deep breath and a ripple of self-aware laughter. At one point she concludes a sprawling 16-minute explanation of the album with: “I think this record is sort of about the cosmos. You might think it’s about whatever.”

The bulk of Batflowers was written over the last couple of years, but the song that brought it all together only came recently. Last November, after months of “trying and trying” to assemble an album, Washington walked past a stack of zines outside a vintage shop in Los Angeles. On the front of them was the text “BAT FLOWER”.

Those two words felt like they unlocked the entire record’s identity, she says, and everything else fell into place. “I love it because it’s everything all at once. It sort of sounds dark and spooky, but it also sounds beautiful and blooming, and it also sounds a bit stupid.”

That day she started work on a song with a friend, producer Jason Wu, titled Batflowers. In February, on a layover in LA, the pair met up again to finish it. “Then I came home and the whole world shut down,” she says.

Washington finished off the record – including teaching herself to animate the video for Dark Parts herself – at home in lockdown. Did she consider delaying its release?

“Oh god, totally,” she says. “But then, 2020 went on and on and on. And I have this rule of thumb which is whenever I look at anybody doing anything ever, I say to myself, ‘Are they doing this to give something?’ And I mean really give it, not to pretend – or to take something.” Washington wanted to give, and so she forged ahead.

“For me, I had to make this record because I didn’t know what else to do! I don’t have enough money to donate millions of squillions of dollars, I’m not Celeste Barber, I’m not that size of artist. I’m just me,” she says. “And so the only thing that I could do was make this.”

It comes back to her new approach. “The thing about being an artist is I used to be really sad. So when I would sing, sometimes – not all the time – people would cry. And that’s because when I get it all right, I’m a good artist. So I guess the question of this album was, OK, what if all of that was the same, except this time, I’m happy? Could I make other people happy?

“Because if that’s a job, I want that job.”

• Washington’s new album Batflowers is out 28 August through Universal