The comeback queen is the perfect protagonist for a musical, say The Cher Show's stars who, led by Arlene Phillips and Oti Mabuse, are embarking on a mammoth UK tour You could call them a triple threat. Debbie Kurup, Danielle Steers and Millie O'Connell all play Cher in a new musical about her rise to fame. The Cher Show presents the singer at different points in her career, with versions of her character called Star…