Miyabe Kingo wrote in an English-language letter the phrase “a sharp zurusona wife” to describe the woman whose house he boarded at. "Zurusona" seems to be the insertion of a Japanese word written in romaji into his otherwise English sentence, which he felt best described her to the Japanese reader rather than writing a fully English description. What does it mean?
I tried looking it up under these spellings ずるそな、ずるそうな、 even づるそな、づるそうな but the only thing I found was 狡(ずる＝cunning deed; sneaky person). Can 狡 be turned into a form that might be romanized as "zurusona"?