The amounts are not for any onboard purchases! They have told her that the charges are for the 'credit hold' so she hasn't secretly been sneaking off to the casino and spending the money
They have agreed that she did not spend this money, they were just making sure she had available credit on her card. She is annoyed because they then told her it would be 3 weeks to get the money credited back to her account.
Anyway, thanks for the replies. I guess if nothing else they should warn people that this is their routine business practice so people don't get a nasty surprise when they see the charges on their card!