The 28-year-old singer was widely praised for her tribute to The Sound of Music at the 87th Academy Awards in February, but the acclaimed 84-year-old composer told The London Times he hated the medley.
"She was a travesty," Sondheim declared of the pop star. "It was ridiculous, as it would be from any singer who treats that music in semi-operatic style. She had no relationship to what she was singing. What people liked was her versatility."