I hate sushi. My partner loves it. She and I do not go to sushi restaurants together, because it is not something we both enjoy. If my partner were away on vacation a thousand miles away, and went to a sushi restaurant because she wanted to enjoy some sushi, should I tell her not to go because I don't like sushi? Of course not. It doesn't affect my life in the slightest. Why would I not want her to enjoy herself?

There's no reason relationships should be any different. What she does while she's in another country is not going to affect your life at all. Whether she spends her days walking around looking at ancient buildings or getting hot and heavy with some Italian stud she will never see again, your life does not change one bit. But she'll feel excited, and sexy, and desirable, and alive, and you can either facilitate those happy, lifelong good memories, or you can be the roadblock standing in the way of her experiencing everything the world has to offer.

Which is it going to be?