If I buy a new iPhone in Italy, will I be able to use it in the USA when I return?

Subsidy locks can only be removed by the carrier to which the phone is locked, so, if you bought a locked phone in Italy, it would be the Italian carrier to which it was locked, that would have to remove it, not Verizon. If you buy the phone directly from an Apple Store, it should be unlocked.

How long is your daughter going to be in Italy? If it won't be very long, I'd suggest she buy a cheap basic phone for calls and texts. Any iPhone purchased in Italy will only have a warranty in the EU. It will have not warranty coverage in the U.S.

Either you misunderstood what you’re being told, or whoever is telling you that doesn’t know what they are talking about.

Verizon can’t “unlock” a phone you purchased in Italy. If you buy an unlocked phone directly from Apple, it should work on Verizon’s network. It will NOT have warranty coverage in the US. It will not have a mm wave antenna so will not have that capability.

The staff should know better, or maybe you did not really understand what they were saying.

If you purchase a phone in Italy, and you want to use it in Italy, it is going to be locked to an Italian carrier. If you want to set up the phone with Verizon in the U.S., the phone must first be unlocked by the Italian carrier.

Verizon cannot unlock a phone that is locked to an Italian carrier, and neither can Apple.

The phone purchased in Italy will not have any type of warranty coverage in the U.S., so that might an important fact to consider as well.

It might be painful to wait, but unless it is a dire emergency, you would do much better to buy the new phone when you are back in the U.S.

All in all, users should purchase a phone in the country in which the phone will be used most of the time to avoid locking issues and no warranty coverage.

I believe that it is no longer legal to sell carrier-locked phones of any kind in the EEC, so all new phones should be unlocked.