#and some of my friends’ grandparents talk strictly in their local dialect too

[the-eclectic-wonderer]

Sophia is very specifically Sicilian and a rural village girl so it's actually logical she would struggle to understand some Standard Italian! Sicilian is its own language and Sicilian Italian is its own regional dialect. I'm 95% the writers weren't thinking of this but it actually makes sense.

Anon, you anticipated me! That’s exactly my hypothesis on why Sophia doesn’t speak proper Italian. In some parts of Italy (especially in the South, or in rural regions) people still speak their dialect before they speak Italian, and prefer their local dialect to Italian in their everyday life. Nowadays everyone learns proper Italian in school, but especially back when Sophia lived in Sicily, she definitely would have spoken in her local dialect only!

Interestingly enough, though, most of the “Italian” expressions she uses aren’t actually Italian nor Sicilian in origin (or, when they are, they’re used incorrectly — see using the word abbondanza as an insult). I think this is where her status as an immigrant comes into play: I have to suppose those words and expressions are part of the (Brooklyn) Italian-American vernacular, and considering she’s been speaking that vernacular for most of her life, it’s not surprising that she defaults to it. I’m afraid I don’t know enough about Italian-American slang to properly verify that, though!