Kelly has performed with the English National Opera for over 30 years. Her roles at the ENO have included Marcellina in Mozart's The Marriage of Figaro and Mrs Grose in Britten's The Turn of the Screw.  In 2009 she starred as Régine Saint Laurent in the premiere of Prima Donna, written by Rufus Wainwright. Reviewing the performance in The Telegraph, Rupert Christiansen described Kelly as an 'amazing chameleon'. She appeared as Pat Nixon in John Adams' Nixon in China at the Metropolitan Opera in New York City in 2011. The New York Times described her performance as 'wonderful'.
Film and television
Kelly's recording of Verdi's La traviata was featured in the 2005 Woody Allen film Match Point.  Recordings by Kelly including a performance of the aria Senza Mamma from Puccini's Suor Angelica appeared on the British ITV television series Inspector Morse.