Here’s how a high school heroine is supposed to behave: She’s shy and responsible, a Cinderella in sneakers. The world — and her parents — might be cruel, but she’s an angel. Her teachers love her. So will her crush, once he knows her name. Maybe she’s artistic or adorably poor. She’s definitely a virgin. Let her best friend be the loudmouth; our dearie is as sweet as a sugar cookie, left un-iced so you can decorate her to look like yourself.

And then there’s The Edge of Seventeen’s Nadine (Hailee Steinfeld). She’s a monster, a girl born into her own nightmare who refuses to wake up. She chooses to live in hell, a decision writer-director Kelly Fremon Craig finds both painful and hilarious. In Nadine’s first scene, she stomps down the hallway in her puffy blue jacket and high-tops, flops next to the desk of her history teacher, Mr. Bruner (Woody Harrelson), and announces she’s committing suicide. A bridge plunge, perhaps? Mr. Bruner reluctantly closes his book and says he’s considering death, too. If his alternative is more time with her, “I would rather have the dark, empty nothingness.” Ouch.

Nadine’s not just a loudmouth — she’s the film’s only mouth. She sucks all the oxygen from the room and spits back flames. One person in Nadine’s blast radius, her best friend, Krista (Haley Lu Richardson), the kind of gentle, golden princess who’d usually be the star, holds back her hair when she gets booze-sick and attempts to keep her calm. Most people, however, like her mother (Kyra Sedgwick), her popular older brother, Darian (Blake Jenner), and her entire school just keep their distance.

She’s a unique combination: the loser/bully, a rare beast almost never spotted in female form. Why is Nadine so angry? Craig doesn’t feed us a pat psychological answer. Yes, Nadine lost her dad (Eric Keenleyside) when she was 13. But in a flashback, we learn she was miserable as far back as second grade. Even Mr. Bruner is done accepting her father’s death as an excuse. When she tries to use it to weasel out of forgetting her homework, he waves her away with, “There’ll be other opportunities. Your grandparents can’t stick around forever.”

The entire movie is a trigger alert, a comedy where a girl sets her safe space on fire. School is torture. Home is worse. And now it’s time to destroy her heart. Nadine mocks awkward Erwin (Hayden Szeto) for liking her, but swoons over the pretty-boy heartbreaker (Alexander Calvert) who works at the pet store. Craig flirts with happiness. When Nadine accidentally-on-purpose runs into her crush, Nick, in the tropical fish aisle, the glow is Baz Luhrmann’s Romeo + Juliet and the soundtrack is Spandau Ballet’s “True,” made famous at the school dance in Sixteen Candles. But Craig isn't going for cute. Nadine and Nick share a gut-churning scene where she drops her armor for someone who couldn’t care less about the soft heart underneath. Please, please, please, Nadine — pick up your battle-ax.

The Edge of Seventeen needs Hailee Steinfeld storming through the flick. She knows how to play tough — she won a Best Supporting Actress nomination at the Oscars for True Grit when she was just 14. She pulls off the trick of being both wild and natural, squaring her shoulders and ignoring the camera like a lioness in a nature documentary preparing to pounce.

Next to her, everyone in the film is a marshmallow. We can’t help grinning as Nadine conquers the squares — even when she’s acting like Genghis Khan by ordering Darian and Krista not to take each other to prom. Nadine doesn’t deserve our love. But she commands it, even when she throws her shoe across a restaurant to cow Krista into refusing the date. “OK, that was weird,” says Krista, cutting our shocked laugh down to size.

The Edge of Seventeen is forever tricking us into chuckling at things we shouldn’t, like when Nadine wounds Erwin twice: once for being attracted to her, and again for daring to protest, “You don’t say that stuff to a man.” Harrelson’s Mr. Bruner is the only character who dares to match her blow for blow. His brutal punch lines make us gasp. Still, Harrelson speaks so deliberately that his insults sound educational, not unhinged. They keep the film surprising and distract us from Craig’s insistence that boyfriends equal happiness, a trope from the old teen movies she’s upending.

Ultimately, every high school flick uses classroom traumas to teach us to be kind. We want Lindsay Lohan to reform the Mean Girls, we want Pretty in Pink’s prepsters to leave Molly Ringwald alone. What makes The Edge of Seventeen special is that it teaches the same lesson, only inside out. It’s easy to root for victims, to cheer Cinderella’s triumph over her cruel sisters. But Nadine forces us to care about the bully, too — to sit with her when she’s sobbing, “How do you like me? What’s wrong with you? I don’t even like me.” At a time when judgment and self-righteousness outrank forgiveness and empathy, Nadine is the heroine we need.