Hi tmc,
I don't know how well traveled you and your family are, but here are some things to keep in mind as a reminder or be aware of...
Call her/your bank to alert them of your daughter's travel - even for travel through the "airport" - say she's transferring through Heathrow and on to Italy - If she wants to buy something at the airport, her card may be declined. Best to give "all" countries she'll be going through. That is what I do. Never had a problem.
If your bank has a somewhat decent exchange rate - (Euro has been at a good percentage lately), maybe send her off with 100€-150€ for her first week until she gets acclimated. TDBank has a decent exchange rate compared to other banks for getting euro ahead of time. And, if you're a customer, you don't have to pay a high fee on top - fee is nominal.
She will get a better exchange rate at a Bancomat (ATM.) It's a good idea to try to get funds from a (ATM) Bancomat attached to a real bank (during banking hours) if at all possible.
A good reason for this is - in case the transaction goes awry and/or her bank card gets eaten. She then goes into the bank and has them retrieve it. If she is getting Euro from an outside machine, make sure she covers the number key pad with her hand. (Things should be okay, but, it's always good to be aware of things anyway.)
Also important to know is "the balance in her account" - meaning some banks allow only a certain amount of Euro to be withdrawn. But perhaps she won't be withdrawing 250€ every other day, lol.
Another thing are the "fees" imposed by your bank - to withdraw. That can make or break a balance. So, it's good to know ahead of time/keep track what your bank will charge in terms of fees - like a "foreign ATM fee" and of course the exchange rate.
Other points to consider and remember - Any time she uses her debit card, make sure she does not choose DCC - this will incur a higher exchange rate. Always choose Euros. Stay away from high percentage rate exchanges at the airport, Travelex or other "non" banks.
Does she know about or would she comfortable using a money belt under her clothes? That's for deep storage of extra money, credit card or PP if she will be carrying it around. (Never put anything of great value in a backpack or backpack purse.) Not her phone either. And, please tell her to not hang her bag on the back of a chair or put it on a table top. While going about, she can "lock" her bags with some type of carabiners.
If at all possible, maybe? take two debit cards - with two different numbers. If she is taking a non FTF credit card, do not use that to get money - fees and rates are high. Only in a dire emergency for that. Otherwise credit card use for regular "credit" transactions will reflect the "rate of the day." Cap One and a few others have no FTF, and the exchange rate for purchases is fair.
I hope she has fun!