It would be a fallacy to deduce that the slow writer necessarily comes up with superior work. There seems to be scant relationshipbetween prolificness and quality.
Art and society was a lot more subject to sexism 50 years ago than it is now. Since that period, there have been plenty of very good female painters, 2006 Turner Prize-winner Tomma Abts among them. How much history needs to pass before an artist is called 'great'? That is the real question.