International coverage for study abroad

Download the airalo app and compare its rates with other international data plans. It uses an e-Sim so no need to remove the one from your current wireless service. I used it for three weeks in Ireland and the UK and service was flawless.

Requesting her device be SIM unlocked is definitely a good place to start.  Contact T-Mobile via 611 or through Facebook or Twitter through DM to get the SIM Unlock process started.  Having a local SIM for calling locally where she will be will help a lot as some colleges can require local numbers for school services and contact.  WiFi Calling can be a good way to use her US number but make sure the device stays in Airplane mode with WiFi turned on.  That way, she can send and receive texts and calls from the US like she is actually in the US.  Just don't let any of that hand off to cellular because that can get expensive really fast.

EU carriers have some great international calling rates, even on prepaid services.  Vodafone was the last one I personally used and calls to North America were 5p (5 British Pence) a minute on the most basic of prepaid plan that covered all of the EU.  

Tmobile plans aren't meant for extended International roaming and usually gets flagged after 90 days and can be closed.

I suggest unlocking the phone and using a local sim for calls in Italy and check out Google voice rates to call the USA from Italy

@drnewcomb  has a pretty decent amount of travel experience with TMO..if he gets a chance he can probably answer some of your questions along with a list of Dos and Donts

this will more than likely be one of the things he points you to for roaming hints

https://docs.google.com/document/d/1eYMuPEbQIcxxxDJBlG8p9FYUT9jdPDIg2-PtG40uJk0/edit