It helps establish the idea that Didion's experiences in New York feel somewhat surreal to her now, like those of a character in a movie.
In the text, Didion says "that is how those years appear to me now, in a long sequence of sentimental dissolves and old-fashioned trick shots". This shows that her experiences in New York feel somewhat surreal to her now. They are brief memories of her time in New York, simple snapshots of her life.
This does not mean that what she says about her life in New York is untrue or fictionalized. It also doesn't mean she feels that she is worthy of being filmed. She is simply stating that her memories appear to her similar to the way a film would of her life. It also does not mean that she believes everyone living in New York feels as though the are stars of an epic film.