Less than 10 minutes into Lady Bird, our teenage heroine throws herself out of a moving car. Christine "Lady Bird" McPherson (Saoirse Ronan) rolls onto the road just to end an argument with her mom (Laurie Metcalf) about where she's going to go to college. For the next half of the movie, she wears a hot pink cast around her forearm like a badge.

In Greta Gerwig's writer/director debut, Christine, who insists on being called Lady Bird, is a high school senior growing up in Sacramento, which she loathingly refers to as the Midwest of California. She wants to move where she can "live through something," which she believes she can find in the form of an East Coast liberal arts college. But her mom, Marion, won't even let her apply to expensive schools. Desperate to break free from mediocrity, Lady Bird slowly abandons her theater-kid friends for a group of rich kids.

With that familiar premise and warm, faded lighting, Gerwig has crafted a sprawling story in which every character is subject to Gerwig's absurd humor as much as her deep empathy. Lady Bird comes alive in its moments of teenage freedom, like when Lady Bird and her friends get stoned and laugh uncontrollably as they microwave snacks in her mom's kitchen, or when Lady Bird and her best friend hide out behind their school's chapel, legs propped up against the wall, hair fanned out behind them as they munch on Eucharist wafers and giggle about masturbating.

Perhaps what makes the movie so uniquely touching is Lady Bird's tense interactions with her mom. It's rare to see a relationship between two complicated women portrayed with such care and empathy. Other characters mistake Lady Bird and Marion for cold and uncaring. But it doesn't take long before we realize that Marion doesn't want Lady Bird to go to college on the East Coast because she can't stand the thought of her daughter being so far away. Lady Bird's friends and family frequently tell her she's self-centered. That might be true, but she's also there for the people she loves when they need her most.

But Lady Bird is endearing because of her boldness, not in spite of it. In one scene, her school holds an anti-abortion rally. A cardigan-wearing woman tells a gym full of high school girls that her own mother was going to get an abortion until "something told her it was wrong." Lady Bird interrupts. "Just because something looks ugly doesn't make it wrong," she says. "If you took up-close shots of my vagina when I'm on my period, it'd look pretty disturbing, but that doesn't make it wrong."

She seems emboldened by her own words, too, because she follows it up with something that's beautiful precisely because it's ugly. "If your mom had had that abortion," she says. "We wouldn't have to have this stupid assembly."

SEE IT: Lady Bird is rated R and is now playing at Bridgeport, Cedar Hills, City Center, Clackamas, Fox Tower, Hollywood, Lloyd, Tigard.