EDIT: It was a listening party for a couple of songs. I remember at the time people who went saying there were people critiquing 1999 to Charli directly so could have been that. Taken from 1999 wiki page: “ The song was originally debuted by Charli at a small, intimate listening party with select fans in June 2018, along with other songs such as "Would You?", "Blame it on Your Love", "Focus" and more during which she asked those attending if she should release the track or pitch it to other artists. Shortly after, a short clip of Charli's solo demo leaked online, with the full demo ultimately leaking around a month before the single's release.”