What is the importance of New York City in the book, Her: A Memoir?

Cara and Christa both lived in New York City on and off during their lives and careers. Christa taught photography classes there and Cara read excerpts of her memoir at a restaurant just before her death. After Cara got brutally raped, she relied on her sister and wanted to be with her all the time. Christa used to travel from New York City to upstate New York where Cara lived for a while to be with her. Christa moved in with her mother after the 9/11 terrorist attack because she didn’t want to live in fear. After Cara’s death, Christa moved back to New York to live with her then boyfriend in Brooklyn.