If the Dominican card is a Visa or MC, she should be able to. However, yes, she should find out from the bank what the fees are first.
Is she traveling on one of the major cruise lines like Royal Caribbean, Princess, etc? If so, when she does her online check-in before the cruise, she will be asked to provide a credit card to establish an onboard account. You can use the Scotia card for that. Onboard, everything she purchases will be charged to her cabin, and go onto that card. She won't use cash on the ship at all, except if she wants to play in the casino or to tip bartenders, etc., onboard. Now in port, that's a different story. I don't know whether shop owners, restaurants, etc., will accept a card from her with your name on it.
The other option, for onboard the ship, is to NOT provide a credit card for an onboard account. In that case she'll have to give a cash deposit/advancement, for purchases, when she checks in at the pier. So, for instance, if she gives them $300 USD, she will have that much to spend during the sailing, onboard. Usually, when she gets near that amount in purchases (say $250 USD), they will alert her and/or not allow her to purchase anything else until she goes to the Guest Services desk onboard and provides additional money. The downside of using cash is that, on the last morning of the sailing, if she's owed any money back, the line can be really, really long at Guest Services. In some cases well over an hour waiting for the balance to be refunded.
I hope that helps
