Greta Gerwig and Lola Kirke navigate the pitiless maw.

Leaving the comfort and familiarity of home for college is scary enough, but entering the pitiless maw of New York City makes it doubly so. In his third collaboration with writer/actress/lady-love Greta Gerwig, Noah Baumbach serves up a scenario in which a naive freshman has a secret weapon: an older pseudo-sister to help her navigate the city as an independent adult. (Gerwig drew from her days at Barnard College for the story.)

Tracy (Gone Girl's Lola Kirke, younger sister of Girls' Jemima Kirke), the student, and Gerwig's Brooke, a freelance interior decorator and self-described autodidact, aren't related, but their divorced parents are planning a wedding that will make their stepsisterly relationship official. Tracy, a sleepy-eyed beauty who slouches through the film wearing the same nubby Fair Isle sweater in most every scene, is hardly an idiot, but she has a blind spot when it comes to Brooke, an effortlessly fashionable Holly Golightly type who talks—and talks and talks—a good game, but has serious problems with follow-through.

While Audrey Hepburn's Holly had the dashing George Peppard to break her fall, Brooke is on her own. Worse yet, she's still pining for the ex-boyfriend who married the rival she blames for all of her problems, because that's how delusional people work: They're never responsible for anything bad that happens to them. So Brooke is struggling to stay afloat in Manhattan, while the tech-dude ex (Michael Chernus) is living large in the cookie-cutter Connecticut suburbs.

Tracy doesn't quite get this at first, especially when Brooke dangles the idea of a waitress job in front of her. First, Our Lady of the Big Ideas just needs to come up with the funds to open her cozy little neighborhood restaurant. No matter that she doesn't have any experience in this notoriously cutthroat field. Where there's a will, there's a way! And the quietly ambitious Tracy has a goal of her own: to join the staff of her school's ridiculously elite literary magazine.

In the best screwball-comedy fashion, Tracy and Brooke's goals collide during a trip to Greenwich, leaving wins, losses, and hurt feelings in their wake. But Baumbach doesn't create flawed characters only to knock them down; just as Tracy turns out to be more opportunistic than she appears, Brooke is a practical creature at heart.

For anyone who ever thought of Gerwig as an opportunist—she made a series of low-budget films with onetime mumblecore kings Joe Swanberg and Mark and Jay Duplass before aligning herself with the Criterion-worthy Baumbach—Mistress America both confirms and refutes that suspicion, depending on whether you "read" Gerwig as being Tracy or Brooke. More likely, she shares traits with both women, and one way or the other, Baumbach has been on a roll since he met her. Even if their latest project together feels like an afterthought when compared to Greenberg and Frances Ha, it's also their most consistently amusing, cleverly self-critical film to date. recommended