Early in the equal-opportunity arrested-development comedy Laggies, three women in their late twenties gather in suburban Seattle for the bridal shower of a fourth. Framed photos convey that the quartet have been friends since childhood. One of them, however, makes it clear that she is not like the others: While the rest of the gang—one of them grandly pregnant—gush and fawn over chaste bridal sex jokes as if Ms. Magazine never changed the world and the winds of feminism had yet to ruffle the Pacific Northwest, Megan Burch (Keira Knightley) wallows in gawky asexuality. Her jokes are as dorky as those of a 13-year-old boy. Knightley slouches in hoodies and an American accent like a skateboard kid, all limbs and scrunchy faces, counting on audiences to forget that the very English, 29-year-old actress now models for posh Chanel perfume ads.

Megan is the laggy under review, a girl who won’t grow up. (The plural, “laggies,” packs more comedy punch, but the title is grammatically incorrect: There is only one exotic late bloomer on display, not the kind of clubhouse full of guy goofballs that characterizes so many comedies of male emotional retardation.) And possibly because Laggies is a comedy of female emotional retardation (and girls traditionally mature more quickly than boys, and yada yada), Megan is—on paper at least—further along life’s circuit than an equivalent male dawdler. She has, for example, a graduate degree in psychology. But apparently she hated doing psychology work, or something. So now she does idiotic, only-in-the-movies work as a human billboard advertising the services of her father’s accounting firm.

Megan does have a longtime boyfriend (Mark Webber), a perfectly pleasant, decent fellow with whom she presumably has an adult sexual relationship. But she feels icky about marrying the man, or something. So when he proposes—at the wedding of the aforementioned friend—she panics. She flees. And, dressed in wedding-party wear outside a liquor store, she meets Annika (Chloe Grace Moretz, always sharp), a 16-year-old high school girl hanging out in a local gaggle of kids while trying to score some booze.

Megan is not quite a cliché runaway bride (Julia Roberts got there first), but she is certainly, tediously cliché adjacent as she hikes up her fancy dress to demonstrate her rusty skateboard skills to the admiring mallrats. Something about Annika’s teen behavior, her amalgam of swagger and insecurity, snark and vulnerability, feels like relief and a return to innocence for Megan. The twentysomething gloms onto the teensomething.

I want to unfriend the lot of them.