Could it be that all the dithering oh-so-New York hipster characters Greta Gerwig has portrayed over the years were just a warm-up act for her emergence as a sharp-eyed, sensitive filmmaker?

Watching the coming-of-age comedy “Lady Bird,” Gerwig’s assured and utterly winning debut as a writer-director, it’s hard to answer anything but “yes.”

Christine McPherson (played by Saoirse Ronan) is a 17-year-old living in Sacramento, Calif. (Gerwig’s hometown), “on the wrong side of the tracks” from the Catholic high school she’s reluctantly attending. Christine — who insists everyone call her Lady Bird — knows she’s destined for better things, if only she can escape the stifling existence of Catholic education and living in Sacramento.

What’s most stifling to Lady Bird is her mother, Marion (Laurie Metcalf), who finds fault in everything her daughter does or says. Marion works double-shifts as a nurse in a nearby psych ward, trying to make up the money lost when her husband, Larry (Tracy Letts), lost his tech-industry job. Marion shoots down Lady Bird’s grand ambitions to go to college in New York, saying that she has neither the grades nor family fortune to make that happen.

Gerwig tells Lady Bird’s story over the course of her senior year, in 2002 and 2003, as the Iraq War is beginning. She deals with her attraction to boys, from theater kid Danny (Lucas Hedges) to anti-establishment guitar player Kyle (Timothée Chalamet). She navigates friendships with longtime bestie Julie (Beanie Feldstein) and her school’s popular girl, Jenna (Odeya Rush). And she confides in Sister Sarah Joan (the great Lois Smith), who sees her love for Sacramento deep beneath her layers of cynicism.

Gerwig, whose writing experience includes collaborations with Joe Swanberg (“Hannah Takes the Stairs”) and Noah Baumbach (“Mistress America,” “Frances Ha”), masterfully captures the pain, anger and love of the mother-daughter relationship. She gives both sides equal time, showing Lady Bird as assertive and unsure by turns, while revealing the concern beneath each of Marion’s cutting remarks.

And “Lady Bird” is blessed with an extraordinary cast. Ronan (“Brooklyn”), who may wind up playing high-schoolers until she’s 40, brings grace and awkwardness to Lady Bird’s emerging adulthood. Metcalf turns the flinty yet sensitive Marion into the strongest performance of her career — which, for someone who won three Emmys for “Roseanne,” is saying something.

What’s most delightful about “Lady Bird” is that Gerwig brings an unabashedly earnest point of view to Lady Bird’s sometimes rocky road to adulthood. The hipster cynicism is gone, and the sincerity shines through.

* * * 1/2

Lady Bird

Greta Gerwig makes an assured directorial debut with this heartfelt story of a rebel daughter and her hypercritical mother.

Where • Broadway Centre Cinemas (Salt Lake City), Century 16 (South Salt Lake).

When • Opens Friday, Nov. 17.

Rating • R for language, sexual content, brief graphic nudity and teen partying.

Running time • 93 minutes.