I wonder if she'll be back (for post #2) and find all was really okay, that it wasn't really taken out of her account twice.
We don't know how long it was between the cruise and her statement from the bank or was it an on line review of her account.
These things occur on credit cards too, but most are not aware of it because they don't depend on usage of a CC the way we do a debit card.
No matter what I use my card for, it's never posted as paid on the day of purchase, but shows a charge pending.