Not to be argumentative, and I definately do not want to put on a "how to use stolen credit card clinic" but your assertion on how experienced "fraudsters" work is not on point with current identity theft issues.
As an investigator I have dealt with hundreds of identity theft cases where credit cards, and other mediums, were used by "criminals." Experienced criminals know which sites have neither of the following: 1. Video coverage of the points of sale. 2. Stores which mandate photo identification to authroize purchases. Criminals know how and when to use a card and will use it until it is cut off. They NEVER discard a credit card that could have any balance available to them.
Given the jurisdictions involved, the cards all have tracers on them. Immediate notifications to law enforcement when a charge hits. Within seconds it is clear if it is a recent charge or an older charge posting against the account.
The single most important issue in this case is was she or was she not on board when they left their last port. If she was, likely a stolen card. If she was not, real issue of security protocols for the cruise line. Should be interesting to watch unfold.