You don't actually "spend" money in cash. You are given a sea pass when you board, which is like a credit card, and everything that you spend on board is charged to your account. At the end of your cruise your account is charged to your credit card. You will of course need cash for spending ashore, which you can get from a shoreside ATM.
Hello Brian welcome back...
As far as your daughter is concerned she can get away, as can you without any US dollars because all you need is your Sea Pass on board and Euros for ashore. If you can concerned about overspend by your daughter you are able to put a cap on her Sea Pass but one would hope that that isn't necessary. Regards ... Ida.
Everything is charged to your room, just like in a hotel. You pay at the end by credit card or by US$ cash. You can put a limit on how much your daughter can spend on her card at the beginning of the cruise, and you can view how much has been spent by each person each day on your interactive TV in your room.