The story of a friendship between a young woman and an elderly widow, Sean Baker’s “Starlet” is a slender, sensitive drama that happens to be set partially within the pornography industry. What these two divergent notions have to do with each other is never clear, but the movie’s performances are so natural and easy and funny that you might not mind.

In one of her first leading roles, Dree Hemingway (daughter of the actress Mariel Hemingway) plays Jane, a frivolous 20-something crashing with pampered Melissa (Stella Maeve) and her boyfriend, Mikey (James Ransone). Jane is professionally known as “Tess Steele” and Melissa as “Zana,” though it’ll be a while before we learn that.

After combing yard sales one afternoon, Jane returns home with an item that turns out to contain something like $10,000 in rolled bills. She tries returning the money (most of it), but its doddering, hostile owner, Sadie, clearly has no memory of it. Nevertheless, Jane forces her friendship upon the woman, perhaps out of guilt, compassion or both.

Aside from the appealing Hemingway, the eclectic cast is anchored by Besedka Johnson, an 85-year-old making her acting debut as Sadie (a producer spotted her in a West Hollywood YMCA). She’s convincing and never sentimental. Maeve (“The Runaways”) nearly steals the show as a petulant, volatile performer, while Ransone (“Sinister”) is very funny as Mikey, a blustering but good-hearted pornographer.

Actually, every character in “Starlet” seems good-hearted, which saps the story of tension and raises the question of why Baker (“Prince of Broadway”) chose the illicit world of pornography for a backdrop. He mostly avoids titillation, but eventually decides that a porn actress is like Chekhov’s proverbial gun: If you introduce her, you’d better use her. The sex in “Starlet” ends up being brief, explicit and irrelevant.