There’s a certain breed of life-size, bare-bones independent movie that consists of nothing more than ordinary people hanging out in plainly lit rooms talking to each other, and it’s a lot harder to bring off than it looks. If a filmmaker slides too far in the direction of threadbare naturalism, he or she can end up with a movie that’s rudderless. (A drama about boredom shouldn’t be boring, etc.) On the other hand, if a filmmaker tries to goose the minimalism with too much repartee, it can sound clanking and false, like a Cassavetes film that secretly yearned to be a sitcom. Occasionally, you see a low-budget indie drama that strikes the perfect balance — the best of the mumblecore films of 10 to 15 years ago, say, or what Kelly Reichardt brought off in the final third of “Certain Women.”

Elisabeth Subrin, the writer-director of “A Woman, a Part” (her first feature), hits that kind of balance. She has made a movie that unfolds organically, and seems no more driven by narrative concerns than a cat playing with a ball of yarn. Yet “A Woman, a Part” knows how to hold an audience, and it’s got a fresh, if commercially limited, subject: What happens when hipsters get old.

It’s also got a fascinating actress. Maggie Siff, who is one of the film’s executive producers, is known for her work on the small screen (“Billions,” “Sons of Anarchy”), and she has a distinctive brainy sensuality, with hints of neurotic anger. (She was made to star in a biopic of Susan Sontag.) I’ve never forgotten her performance as a Jewish department-store heiress in the early episodes of “Mad Men” — she seemed like the kind of woman who could actually be Don Draper’s equal, which is why their flirtation didn’t work out; she was drawn to, and saw through, the caddishness.

In “A Woman, a Part,” she plays Anna Baskin, who is, in fact, a well-known actress on a hit television series based in L.A. When we first see her, she’s griping about having to perform the umpteenth cliché scene in which she expresses inner turmoil by spilling a cup of coffee. Moments later, she stalks away from the set and into her dressing room, with a tell-tale coffee stain, complaining that her character is too empty, too programmed, too much of a cipher. Then she goes home and throws all the scripts she has sitting around into the swimming pool.

Her manager, the wise and understanding Leslie (Khandi Alexander), is African-American, and that’s not incidental: With every breath she seems to be saying, “Girl, you need to calm down, because you are having some white people problems.” And she is. Anna’s criticisms of the show she’s on are valid — and also implicitly, if vaguely, feminist (though it’s not as if women in television have a lock on being forced to play cliché characters). But she also seems spoiled and deluded. (Boo-hoo! Hit TV series can grow formulaic!) And that’s because this is more than a creative tiff — it’s a middle-aged actress’s existential meltdown. What is Anna fighting for? What role does she want to play? Who, beneath the onion-skin layers of acting, does she really want to be?

To find out, she cuts out of L.A. and returns to the rent-controlled apartment in Brooklyn that she’s held onto for years (though she’s supposedly in the process of giving it up). It’s a spacious but scuzzy bohemian pad, nearly empty, and it links her back to her comrades from the ’90s, a troupe of downtown theater people who once formed a scene and are still clinging to the frayed edges of it.

Anna is the one who went off and became successful, but she wonders if she gave up the purity of her art. This is a theme that’s fast becoming an obsession in contemporary drama, echoed in everything from “Girls” to the improv-comedy-troupe tale “Don’t Think Twice” to “La La Land.” The theme is this: Working to become an artist has rarely been an economically nourishing endeavor, but in our era it has become crushing, with life in vital creative urban settings now pricing out the very people it attracts. There are many reasons this is not likely to get easier under Donald Trump.

As a filmmaker, Subrin has the confidence to let a moment ramble, but she’s also a disciplined scene-shaper who jump-cuts her way through the movie (the terrific editing is by Jenn Ruff), so that the audience never feels it’s getting bogged down; each moment has been chosen for us. And the actors are marvelous — one look at each of them, and you feel the decades of backstory. Anna’s old theater chums are desperate and living off the fumes of faded dreams: Kate (Cara Seymour), a blustery British recovering alcoholic just turning 50 (Anna first shows up at her birthday party), who scrapes by leading a confessional yoga class, and Isaac (John Ortiz), an owlishly benevolent manipulator and once-promising playwright now stuck in a troubled marriage, and with a young daughter, who is trying to revive his career by writing a play about…the downtown theater scene of the ’90s. The thing is, it’s a good play — it’s what he knows — and the central character is a thinly disguised version of Anna: a high-strung Connecticut princess who’s the frazzled star of the group. Will she do Isaac a favor and play the part in a reading?

That question never dominates the action; it’s just one of many notes in Anna’s week of drifting around. She slashes her hair into bangs, meets a handsome mensch (Lucas Near-Verbrugghe) she lies to and sleeps with (the former action undermines the latter), and approaches her old friends in a tentative spirit of repair. (Had she betrayed them? Yes and no.) And she wonders what it would be like to ditch the acting thing entirely. Drifting around, aimless and even self-destructive, is what we often do when we confront a moment of change, but “A Woman, a Part” justifies itself through the spirit of its conversation. Though not much happens, you’re more than eager to know what everyone’s going to say next. I’m also eager to know what’s next for Maggie Siff and filmmaker Elisabeth Subrin — who, as this movie demonstrates, both deserve radically higher profiles.