We have an entire thread dedicated to this. Native Italians are white Caucasian, just like the rest of Europe is. Perhaps just a tad darker. People whose skin tone isn’t light or at most tan in color (as in, people whose families aren’t of Italian descent or haven’t been in Italy for several generations) have significantly different social backgrounds than the average Italian.
It pretty much means that if she adds more skin tones (aka more ethnicities/races that aren’t native) she can’t possibly portray their identity correctly. If her MC is native Italian, then they’ll also have a whole cultural and linguistic background that wouldn’t match if the reader made the MC of a different nationality/ethnicity/race. It simply wouldn’t be realistic 
My stance is, don’t worry and go with limited CC @Joanne00 dear