Allegory?

A suggestion.
- The writer represents Godard. He considers three different career paths: writing this movie, writing detective novels or going back to radio. Godard could make movies or make other kinds of movies or go back to being a reviewer.

- The girl represents the audience of intelligent filmgoers that he tries to impress. That's why she reads the book of film criticism in the bath. Critics tell her what she should think. Later she uses the book to cover her ass, telling us what Godard thinks of the critics. The writer character picks up the book, but never reads it, also telling us what he thinks of the critics. That the audience only ever reads the book when naked may imply that the audience don't really have any opinions of their own, just the ones the critics give them.

- The assistant/secretary represents other, less sophisticated types of filmgoers, who don't normally see Godard films. The writer attempting to flirt with her represents the possibility of making films for this audience, but she rejects him, just as the average audience tends to reject his films.

- The producer represents Hollywood and the kinds of films Hollywood was making. The writer/Godard has plenty of doubts about this him/it, but is thinking about trying anyway, if it will impress her/the audience.

- Fritz Lang represents Fritz Lang or the integrity and history of intelligent filmmaking.

- She/the audience expresses contempt for the writer, but we never really get a clear explanation of why. This is much like the feedback a director gets on a film. Many different voices and opinions, but no clear and coherent message.

- Godard thinks that if the producer/Hollywood and the girl/audience go off on their own without the writer/Godard, it won't go well. In fact it will be a disaster. But fortunately the old films of Fritz Lang continue, offering some solace.