06/20/2008 at 08:00 AM EDT
has been tested for tuberculosis during her prolonged hospital stay
, her rep tells PEOPLE.
"She has a chest infection and she had a routine test for TB, which came back negative," Chris Goodman tells PEOPLE.
Goodman also denies a report – in U.K. tabloid The Sun
– that she has been coughing up blood at the London clinic where she was taken after fainting
earlier this week.
The troubled singer, 24, is still undergoing tests and doctors will soon decide whether she is able to keep her upcoming performing commitments. One insider says her chances of performing for Nelson Mandela's 90th birthday celebration in London on June 27 are "50/50."
"She would really love to do the show – she always wants to do these things," said Goodman. "But she will listen to her doctors."