Why did Bruno's mother snap at Bruno?

Bruno's mother snapped at him when he continued to object to their move from Berlin.

'I'm sorry, Bruno,' said Mother, 'but your plans are just going to have to wait. We don't have a choice in this.'
'But, Mother!'
'Bruno, that's enough,' she said, snapping at him now and standing up to show him that she was serious when she said that was enough. 'Honestly, only last week you were complaining about how much things have changed here recently.'