Teen star Billie Eilish on therapy, her boyfriend and how fame has changed her

When teenagers dream of becoming pop stars, I imagine the scene they picture is pretty much this. A matt-black Dodge Challenger pulls up for a photo shoot in a fashionably obscure Los Angeles neighbourhood. A documentary film crew is poised at the studio door to capture its arrival. Inside, a dozen or so creatives wearing baseball caps and black arrange vegan snacks among the vintage vinyl and French fashion magazines; racks of jewellery and rails of designer clothes and shoes fill another entire room. Everyone resembles an ironic extra from Wayne’s World, except for the silver-haired man in a suit guarding the diamonds, who looks as if he’s stepped off the set of The Sopranos.

We’re all waiting for Billie Eilish, the singer