“I think she’s the most fantastic artist, the most fantastic singer,” Olivia Rodrigo said when introducing Natalie Imbruglia to the audience in London. Olivia Rodrigo’s viral dive bar performance of Natalie Imbruglia’s hit “Torn”? Turns out, it was just a rehearsal. On Wednesday, the three-time Grammy winner surprised concertgoers at London’s Eventim Apollo with a performance of the 1997 hit …