There is a moment in Babyteeth where Eliza Scanlen cranks up the music (the spirited strings of Sudan Archives’ “Come Meh Way” cuts through to the soul), rippling her body, limbs akimbo, shoulders undulating, her feet kinetic on the carpet. She dances with the unabashed fervour of a teenage girl without a problem in the world. But that isn’t her reality in this unforgettable coming-of-age film, which follows terminally ill 16-year-old Milla (Scanlen), who falls in love with erratic tattooed junkie Moses (Toby Wallace) – all while her parents Henry (Ben Mendelsohn) and wife Anna (Essie Davis) navigate this unchartered territory.

Helmed by theatre director Shannon Murphy from a script that playwright Rita Kalnejais adapted from her play of the same title, Babyteeth takes a hackneyed premise (sick teen falls in love, thus allowing them to make peace with their grave situation) and offers something completely refreshing. Cliché-free and never veering on saccharine, it is tear-chokingly heartbreaking, unexpectedly poetic and chock-full of pitch-black laughs. Standout scenes include Milla bringing Moses to a chaotic family dinner where her mother is accidentally high and incapacitated on a cocktail of prescription drugs; in another, Henry and Anna question their parenting skills as they witness rat-tailed Moses playfully strong-arming Milla to the floor, straddling her as he tickles her.

And Australian actor Eliza Scanlen is mesmerising. Her open face has the ability to embody a spectrum of triggers of the human psyche. Fresh in our minds from a series of staggering breakout roles: she is a terrifying and sinister presence in HBO’s Sharp Objects opposite Amy Adams; in Greta Gerwig’s Little Women, her tenderness and vulnerability as Beth is heartrending – but one thing they have in common is Scanlen is coruscating and uninhibited.

We caught up with Scanlen over the phone from Sydney and talked about the empowering process of shaving her head for the role, and subverting romantic cancer-teen film tropes…

Hi Eliza, congratulations on Babyteeth. What drew you to the script?
I first met Shannon in 2018 about Babyteeth. I had been sent the script and auditioned, but hadn’t heard anything, and a few months later and I had flown to the states to do Little Women, and funnily enough, Toby Wallace – who plays Moses – was in Massachusetts as well shooting The Society. We had a mutual friend so we ended up hanging out that night and talked about Babyteeth because by that point he had gotten the role of Moses. After seeing Toby, I thought I’d email my agent about it, and at the same time the casting director called me to offer me the role – so it was a really funny coincidence. At this stage in my career you’re lucky to come across something you love entirely, but this is definitely something I fell in love with straightaway.

I read somewhere that you had your head shaved every single day. What was the emotional and psychological impact of doing that?
Once I was in rehearsals I was excited for it be shaven off and really throw myself at the character. Some actors choose to lose a few kilos for a role and most of the time it’s an optional thing, but in order to play Milla the hair had to be gone, but it was really empowering. It was definitely eye-opening too because unfortunately people do see you in a different way, when you’re taking public transport or when you’re out in public, there were some times where people didn’t really want to look at me, and afraid or uncomfortable to be looking at me for too long. When you’re playing a character you’re adding things on and more and more layers to you as a person, whereas here I took a big part of myself away. We all know that we hide behind our hair so to not have that was scary as fuck.

I loved the chaotic family dynamic in the film, it’s kind of messed up and falling apart but comes together in a really sweet and touching way. What was the experience of creating this with Ben Mendelsohn and Essie Davis like?
We had a lot of rehearsals actually, and by the time we were on set we were all quite close. Ben and Essie, they’re two very different actors too. Ben is a very charismatic person and he’ll look at the script and see the lines and will throw it away and has a very intrinsic sense of what the scene needs to be and what a director needs from him, but there’s an unpredictability about his acting style which is really fascinating to watch. On the other hand Essie’s very meticulous and it’s a lot of open communication between her and the director and it was really incredible for Toby and I to witness that.

And for people watching the film, what do you want them to take away in terms of a message about family and family dynamics?
That’s a good question. I think that one thing that people can take is that dysfunctional families are normal, and despite your parents being your parents, they are human beings and it’s a sobering realisation to come to as a young person but it’s inevitable. I think Milla learns to accept her relationship with her parents and their own struggles with their own feelings. But also at the same time Milla comes into her own and she listens to herself at the end of the film and has to take a stand for herself with her own desires.

So there’s a few scenes that really stood out to me. I love the scene where you first take Moses back for dinner and obviously Essie Davis has taken… a few too many drugs. Then there’s also the beach scene at the end, which is so touching and emotional. Which did you enjoy filming the most?
I think that the beach scene was obviously a lot of fun. It was a very windy day so I guess it was less about the lines and more about having fun, but there was a moment that Ben and I have in that scene that was quite heart-wrenching to watch, and the direction I was given on that day by Shannon was to not cry and that was obviously very hard watching Ben cry in front of me. I think there were a lot of moments like that in the film where Shannon didn’t let me fall too deep into the grief of the story and she doesn’t let the audience do that either, so I found that a particularly challenging thing to do.

It’s interesting what you say about not being allowed to fall too deep into the grief of the story. It would have been really easy for a film about terminal cancer to do that, but it never veers on sugary sweet…
Again, that’s Rita and Shannon’s theatre background. The title cards are actually a Brechtian technique that cuts the audience off from experiencing the deep emotion of the scene, so basically her intention was throughout the editing process was to not let the audience indulge in the despair, which is, I think, a really interesting metaphor for life itself. When we’re faced with trauma, we can’t dwell too much in the despair. At some point there has to be a conscientious effort to move forward and Milla seems to be doing that with every inch of her being. She’s got a lot of resilience but there’s also a lot of anger there too which is what I don’t see often in movies like this. You normally just see a young girl who might fall in love with somebody and peacefully wastes away.

And you would be so angry!
Of course she’s angry. I feel like she’s the true embodiment of when someone is faced with something so traumatic like cancer, you fight to the end, and I feel like Milla is very much a fighter in that way.

And for someone like Milla, what do you think draws her to someone as rebellious as Moses?
I think at the beginning of the film their relationship is transactional: he wants her drugs and she wants an escape. And I think it’s a gateway for her to experience life beyond the bounds of her parents, and she has nothing to lose and I think they encourage each other to be better. A lot of people are saying that the relationship isn’t right but I feel like they are really good for each other because he doesn’t look at her with any added sympathy because she has cancer, and it’s very rare that that happens so she holds on to that.

All your previous roles definitely pack an emotional punch, with most of them veering on the darker side. Is there a method to how you choose what you take on?
I guess I’m starting to discover a pattern in what material I’m interested in – it’s always the indie films that I’m interested in, which is wonderful. I find archetype really distasteful, I also just can’t read scripts that are predictable in that way. I just feel really lucky that each role has been so transformative for me and has brought me so many strong relationships in the industry and also personally.

You’ve got psychological thriller The Devil All The Time (Robert Pattinson, Tom Holland, Bill Skarsgård, Riley Keough, Mia Wasikowska) coming up, and you’re psychopathic in Sharp Objects – is there an emotive response you’re trying to get out of your viewers or is it more just that you love undertaking the process of these complex characters?
I’m continually being drawn to darker characters, but I really enjoy the process. I enjoy writing about characters before I get on set and creating a world. It’s really fun.

Babyteeth is released in cinemas on 14 August