How does Maria react when Bruno asks why Pavel lied about being a doctor?

Maria becomes nervous when Bruno poses this question.

Maria's face froze a little and she didn't say anything for a moment. Instead she looked away and licked her lips a little before
nodding her head. 'I see,' she said. 'And what did he say he was really?'
'He said he was a doctor,' said Bruno. 'Which didn't seem right at all. He's not a doctor, is he?'
'No,' said Maria, shaking her head. 'No, he's not a doctor. He's a waiter.'
(page 137)