It is possible that she set up a cash account with the purser's desk.
To do this you deposit $250 or more with the purser's desk and use your ship's card until the money runs out or you are notified, by customer service, that you will need to add more money to your cash account.
You still use your card for all purchases but you do back it up with cash, on deposit, instead of using your credit card to back up the ship's card.
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