Yes, you can give her a prepaid VISA card, but be sure that it has a chip/PIN factor; that's needed for most cards in Europe. (A better bet is a "traveler's check card", which will cost you a bit more, but is more likely to work properly. You can get them at AmericanExpress and Mastercard (
https://www.travelex.com/travel-money-card), as well as at AAA.com. Do note that most of these cards have withdrawal fees when used at ATM's, so if she gets cash she should get fairly large amounts at a time.) If she is planning to travel in the West, she should carry some small-denomination Euro bills, as some retailers in the West still balk at taking CC for small purchases. It will be difficult to find a Euro card in the US unless you are in a major city, but not impossible, and doing that will save her the usual 1-3% currency conversion fee. US banks will sell you Euros. but in many areas branches will not customarily stock them; you should call first, and you may be sent to the main office in your area.
Remember above all that Ireland is DAMP. As a add'l Xmas gift, I'd suggest a gift card from WinterSilks.com. (I don't work for them, LOL.) They have a very nice selection of comfortable silk long underwear that takes up very little space in baggage; worth its weight in gold when traveling, because it is warm when outdoors but not too hot indoors, and washes out easily in a hotel sink. I would also suggest a rain cape if she's willing to wear one; this one is affordable and quite nice,
https://www.amazon.com/LINENLUX-Pon...utdoor/dp/B079JBWM3Q?tag=topluggagereviews-20 (capes are great because wind doesn't flip them, and if you want to sit down on a stone wall while touring some castle ruin, your tush will stay dry.)
PS: my favorite travel laundry/shopping bags are from IKEA, if you have access to one. Best laundry bag ever is an IKEA Knalla zipper bag; folds easily, weighs nothing, stands up square, dampproof, and even has a vent, all for $3. For groceries, the thin nylon Knalla shopping bags are excellent, too, $2/ea. (These are not the large blue Frakta bags; these are smaller and come in red or black checked pattern.)