No other source lists "another woman". That's an odd detail to get wrong after so many years.
Kennedy's police statement says,"There was one passenger with me, one Miss Mary [Kopechne], a former secretary of my brother Sen. Robert Kennedy".
Good catch.
As with all these “political cover-ups” the first responders get the facts and then their bosses start the cover-up after they have been “contacted” by the politicians.
So, it is very difficult to get the facts without interviewing the first responders (privately).
That is how folks here figured out the official lies in the Vince Foster case, btw.