That sounds like the Vatican City located in Rome, Italy. There should be plenty of holy water and crosses there. And she could even get them blessed before her next trip.
The next letter came just last week and said,
"I've finally arrived in a dark region nortHwest of a mountain range. As expected, I've already used the supplies I picked up last Week to keep unwanted guests away, though an invisibility cloak helps, too. Good thing I've been practicing my Protego charm! The other daY I had a close run-in with a certain notorious being, but escaped just in the 'neck' of time!
I wonder if she dropped by Transylvania, Romania which is by the Carpathian Mountains. That area is often associated with Count Dracula. Hopefully she will come back in one piece and not as a creature of the night.
I'm definitely getting tIred of all the traveling, but I'm hoping I'll be able to return to Hogwarts soon. I've got just one more Quick trip to make, and I'll send an owl as soon as I find what I'm looking for."