Generally, JPN people love Italian food and if they live somewhere like Tokyo they can get access to genuine Italian food. Italian food culture is one of the reasons that JPN people develop a very positive impression of Italy and Italians. However, living in Italy and eating Italian food everyday is a different issue. A few years ago I spent an extended vacation in Italy and travelled with a JPN woman. When her visa ran out she decided to return to JPN and came back a few days later with a suitcase of JPN cooking supplies. She was a very "international", very sophisticated and loved Italy and Italian food. But your Asian restaurants and grocery stores are not going to be an adequate replacement for JPN food. We were based in Roma and Firenze. I think JPN people would generally prefer food from the South, the coastal regions or the islands. I don't think she could have survived an extended stay in Toscana without having access to the terrific central market. My companion would sometimes make a sorte to a local Chinese restaurant in Firenze to get a noodle fix - very low quality food. The sort of place I would not even think of entering - but she was desperate. I strongly recommend introducing your friend to the local food markets.
If you move forward with your plans, you should note how much research and preparation she makes in advance of the trip. What ideas does she have about studying/working? what interests does she want to pursue? This will give you an idea about how much of self starter she is, or how much of a passenger she will be.
If she does attend a language school, she will meet a circle of international friends some of whom will likely be JPN. That may help with homesickness and boredom, but I think it is also important for you and her to develop a circle of local friends and mix with your family.
It has been an amazing transformation. A benefit(?) of globalization. There are more Pizzerias within 5km of my house in Tokyo than there are in downtown Florence!
