I know that correctness is determined without regard to punctuation and capitalization, but it would be helpful to me to see the formally correct writing, including capitalization and commas where appropriate. E.g., "How is work, sister?" would be better in the English. Would "Habari za kazi, dada?" be the correct way to write it in Swahili? Because I don't know the language, the comma makes the meaning clearer to me. (I had guessed it was asking about a sister's job, not addressing the sister.)
This is just a guess, but because of the fact that it would seem that adjectives come after the nouns they modify, you probably would want the vocative comma there. Otherwise, it comes out sounding like "sister work", describing a kind of work that's classified as "sister" somehow (as opposed to some other kind of work... like... I dunno'... possum work... lol). I've only been at this for a few days, so someone please correct me if I'm wrong, but that's my guess.