Greta Gerwig, who wrote and directed the superb new Lady Bird, has been waiting quite some time for her big moment to come. It’s here now.

A decade ago, she co-wrote and starred in Joe Swanberg’s indie romantic dramedy Hannah Takes the Stairs, which landed her squarely in the middle of the Mumblecore scene. A year later, she shared both writing and directing credit with Swanberg on Nights and Weekends, where they starred as a struggling couple.

As a next step, she teamed up with Noah Baumbach for Greenberg, an upscale Mumble-inspired affair about an emotionally-stunted man (Ben Stiller) housesitting in LA who falls for his rich brother’s assistant (Gerwig).

From there, she flirted with the mainstream, but returned to work with Baumbach in Frances Ha, for which she also co-wrote the script. because it felt like she seized the opportunity to tell a version of her story as a never-quit aspirant in the soul-crushing film industry. She and Baumbach collaborated again in 2015, on Mistress America, and then she joined forces with Rebecca Miller for Maggie’s Plan. In the meantime, she has appeared in many movies, both Hollywood and indie.

Gerwig’s career has been building as an actress who also writes and directs, but in Lady Bird she’s in complete control (although she isn’t one of the film’s featured performers). It finds her settling in at the helm of her most nakedly personal story yet.

Lady Bird is the name Christine McPherson (Saoirse Ronan) has given to herself, a rebellious thumb to the eye of her mother Marion (Laurie Metcalf), a domineering woman who tough loves her husband Larry (Tracy Letts), son Miguel (Jordan Rodriguez) and Christine into submission. The family drifts through life in Sacramento, Calif., but Lady Bird pushes against the constraints of her senior year at Catholic school, and dares to imagine escaping to perceived freedom of the East Coast.

Gerwig guides us through this world like a native, because it literally is her coming-of-age experience. She presents Lady Bird as a headstrong girl with one foot firmly planted in adulthood and the other free of contact with the ground, but her fear and anxiety about what comes next exerts its own very real gravitational pull.

Ronan embodies all of the character’s defiance, self-criticism, intelligence, and self-centeredness in a way that should be painfully recognizable to any parent of daughters in the audience. The specificity of the character makes every response to her ring just as true, although that should take nothing away from the efforts of the amazingly talented ensemble cast.

Since catching the film at the Toronto International Film Festival, I have been tracking the buzz for Metcalf, which has definitely reached a fevered pitch. She’s now the odds-on early favorite to snag the Supporting Actress prize at the Oscars, but focusing on either her or Ronan (who plays every scene like she’s wiggling around in a worn pair of woolen socks), draws attention away from Lett’s quietly soulful turn as a father facing the depressing reality of obsolescence.

Of course, the real credit belongs to Gerwig, the narrative mastermind who intuitively knew that she didn’t need to play any of these situations broadly, in order to get the laugh or make it family friendly. There’s never a moment where you sense Gerwig forcing Ronan to imitate her, like we’ve come to expect from Woody Allen’s stammering avatars. Lady Bird captures and shares the universality of Gerwig’s experiences and presents a true reflection of paths not taken for both children and parents.

This is a revolutionary moment of sorts too, when you consider that we’re talking about a story with a female protagonist who doesn’t wield a bow and arrow, prance about in a superhero costume, or cater to the tastes of a privileged demographic (males between the ages of 18-25). Lady Bird’s story truly belongs to all of us.

What this does for Gerwig is elevate her a bit from a talented pack of multi-hyphenate contemporaries like Amy Seimetz (Steven Soderbergh television series The Girlfriend Experience) and Brit Marling (Another Earth, creator of The OA), themselves on the verge of fearless breakthroughs. Lady Bird, in a year without a clear front-runner, could take flight and usher in the kind of impactful changes in the film industry we’ve been dreaming and whispering about for the last decade. Let’s hitch a ride with Gerwig and see high far she leads us. (Opens Friday) (R) Grade: A