We have a PO Box for our mail for this reason. It is relatively rural where I live. To get mail delivered to our physical address, we would have to set up our own box or buy a space in an established box near our home. Mail theft is pretty common here, especially around the holidays.
I’m so sorry your friend had to experience this. Does she have photos that she can share on a local online group/forum where they were stolen? It might be worth sharing them to try to recover them.