When Buckley was seventeen, she went to London to audition for drama school but was rejected from her first choice. Distraught, she walked into an open call for a BBC reality show called “I’d Do Anything,” a singing competition in which the winner would star as Nancy in a production of “Oliver!” She got on the series and won second place, after one of the judges, Andrew Lloyd Webber, championed her. “He’s always stayed in contact: ‘Come and have a cup of coffee,’ ” she said. Years later, she auditioned for the movie version of Webber’s “Cats,” but was relieved not to be cast. “I don’t know how fluidly feline I would have been,” she said. “I’d be a very stagnant, boxlike, kind of anxious cat.

In the new Charlie Kaufman film, “I’m Thinking of Ending Things,” which premières next week, on Netflix, Buckley plays a young woman who drives to the country with her boyfriend, Jake (Jesse Plemons), to meet his parents. Or she may be a figment of his imagination, or the hallucination of a high-school janitor. The movie is, to use the year’s most well-worn adjective, surreal: characters suddenly age thirty years, or break into songs from “Oklahoma!” “The first-ever note I got from Charlie, even in the audition, was ‘This girl is molecular,’ ” Buckley said. “I’m, like, What the hell does ‘molecular’ mean?

During filming, she and Kaufman would e-mail odd inspirations back and forth: Anne Sexton poems, A.S.M.R. videos. Did she ever figure out what “molecular” meant? “I am a molecule of myself,” she speculated, of her character. “But I’m made up of atoms that Jake has created, which then explode and disintegrate.” Flustered, she blew a raspberry. “I was crap at science.” She had a week left in solitude in her hamster apartment, then four days of shooting “Fargo,” opposite Jason Schwartzman. “We have swabs every three days,” she explained; the protocols would allow the actors to play their scenes without social distancing. “We’re molecules!” she said, lighting up. “Finally, I get to be a molecule! This is what he meant! I get it!” ♦