The 27-year-old was recently booed off stage by the 20,000 strong crowd after a performance where she was heckled by fans.
Band Zemlja Gruva were also on the bill and one of its members Ana Zoe Kida said to UK newspaper The Sun: 'Four British bodyguards simply pushed her to step up on stage.
'She did not want to and was making a scene trying to escape them. It was distressing to see, she obviously needed help.'
However a spokesman for the star has denied the claims and said she voluntarily went on to the stage with a friend.