Greta Gerwig.

Though Greta Gerwig has outlived the heyday of "mumblecore"—a genre distinguished by low budgets and a rambling discursiveness—any movie she is in seems to become as much. While Lola Versus bears many hallmarks of a more traditional romantic comedy, the actress at its center consistently carries it beyond the bounds of its own ambitions.

Lola Versus is a quirky indie flick with dreams of being a big, broadly appealing romantic comedy—it’s not so different from last summer’s Friends With Benefits, a big, broadly appealing romantic comedy that wanted to be quirky. The titular Lola, played by Ms. Gerwig, gets dumped by her fiancé by the end of the opening credits. She then relies on her zany single friend for support as she tries to navigate the New York dating scene, expectably developing a crush on the male friend who’s been there all along. Put Mila Kunis or Emma Stone in Greta Gerwig’s role, and move the setting to a backdrop more cinematic than somewhere in crypto-Downtown Manhattan or North Brooklyn, and, voila, you have a movie that pulls in upward of $30 million on opening weekend.

And yet Ms. Gerwig’s pushes Lola Versus into riskier territory. For much of the movie, Lola is a fully realized character only insofar as she resembles the public persona of Greta Gerwig. Like Florence in Greenberg (our introduction to Ms. Gerwig’s off-beat style and grace), Lola moves listlessly, speaks with a flat affect, and looks at men less with lust or love and more with a why-not boredom. While the role is no stretch for Ms. Gerwig—she’s played it before, and plays it often—her presence in it changes the movie in a manner its writers (Daryl Wein, who also directed, and Zoe Lister-Jones) likely did not anticipate. The script indicates that Lola falls, hard, for her male best friend, Henry (played by Hamish Linklater); the performance indicates that Lola is curious what it would be like to sleep with Henry, in part as a means of destroying the social circle she and her ex share, and does so in a moment of weakness.

That’s not to say that Lola Versus is schizophrenic. The two Lolas—the script’s hopeless romantic and the one who appears on-screen, uncertainly clumping through life—actually complement one another in a portrait of a woman who has no idea what she wants. Ms. Gerwig’s performance is most effective in Lola’s interactions with her ex, Luke (Joel Kinnaman). She, understandably, harbors conflicting feelings for the man who ended her engagement. And thanks to Ms. Gerwig’s fundamental anomie, Lola seems to be deeply saddened when the script tells Ms. Gerwig to flaunt her character’s sex life to Luke—she mopes even when they end up back in bed together.

While Ms. Gerwig does it all so easily, she is alone when she takes her character around an unforeseen corner in the story, falling into mania (she steals from a liquor store, and storms the stage at a strip club) in a way that’s written as funny but plays as grotesque. Character is sacrificed to the notion of signifiers throughout. It’s cool to have a heroine who likes strip clubs and drinking and eats things she shouldn’t. It’s harder for that character to do something real.

And Lola Versus does play like a cool-kid version of an old romantic comedy: it begins with heartbreak and moves toward the heroine’s fulfillment. It gets all the old satisfying beats right; there’s a narrative reason, after all, why the protagonist needs a best friend/confessor, and why there need to be obstacles in the path to happiness. We haven’t come that far from My Best Friend’s Wedding and the like, and the best romantic comedies wring real emotion from obvious fakery. Perversely, the "realness" of Lola Versus is its greatest stumbling block. Realness is in quotes here as the writers and director clearly believe they’re portraying a young person’s reality by having Lola stride down a beach covered in garbage, or eat hot wings at the strip club, or have inane Styles-section-trend-piece conversations with her mother about freezing her eggs. Were everything in this movie that strives to portray the reality of a hip woman dialed down from 11, this movie would be able to give a better notion of who the enigmatic Lola character really is. The film could be what it aspires to be: a cool person’s romantic comedy. It’s not cool to try too hard, after all.

Ms. Gerwig is not a big enough star to headline the big-budget version of this movie; nor, really, would she fit in there. She is not an actress who has, yet, stretched herself to fit dramatically different milieus—until she ages out of the part, she’ll be playing cool single women with something broken inside. Certainly there are many performers who’ve stuck with one sort of role. The joy can be in the variation, the discernible but subtle shading. But Lola Versus, though eminently watchable, doesn’t ask Ms. Gerwig for shading so much as an entire emotional rainbow, racing through a range of ever-changing motivations occasioned by the script. This role bears all of the problems a Greta Gerwig character could face, wrapped up under 90 minutes. The actress nearly pulls it off—but, ultimately, Lola has too much against which to struggle.

Lola Versus

Running Time 87 minutes

Written by Daryl Wein and Zoe Lister-Jones

Directed by Daryl Wein

Starring Greta Gerwig, Joel Kinnaman and Hamish Linklater

Three out of four stars