Hello,
I think you are talking about Sugar Changed the World.
"Nina was always a mysterious figure in the family: beautiful as a movie star, cosmopolitan and elegant, with wide Slavic cheeks. She spoke only Russian, though she lived much of her adult life in Tel Aviv. There were rumors that she came from nobility and that she had once been very rich. She and Avram were thought of as a glamorous couple—he the charming man with his head in the clouds (in Yiddish the word for that kind of person is luftmensh, "air man''), she the mysterious beauty who had given up everything to be with him."
Answer:
In this passage, the author presents background information about Nina by providing us personal information about her and historical facts about her life; he also describes the mystery, controversial and weirds topics that have been taking place during her life.
His 2nd porpuse was to show how Nina was able to mislead people: We can see how she was able to trick people, she was a liar: she spoke Russian, but she knew speak Hebrew.
Next time, please, add the passage. :) Thanks!