Ahh yes Leni Riefenstahl... it was a shocking HSC question last year =)
I think that when assessing Leni's impact on German social and cultural life, you could start by saying her role had a significant impact, but Leni's role alone did not bring about all the changes.
I think assessing her two films Triumph of the Will and Olympia is the best way in terms of the impact of the 'propaganda or art' value on the German people. Simply put, (assuming she did have an impact), was this impact in terms of promoting Nazi idealogy or the artistic 'Expressionist' movement?
Then you could approach and assess each area. What features of her films promoted Nazi idealogy (Eg. Use of Wagnarian music, messianic images of Hitler, choice of selective camera angles and editing, etc). How and to what extent did this contribute to Hitler's idealogies, in particular, 'Volksgemienschaft'[unified community] idealogy.
What features of her films promoted artistic 'Expressionism'? (Eg. Focus on 'Cult of the Body' idealogy, repeated gynamastic poses, slow motion of athlete's muscular movements). To what extent did her innovative film techniques promote Germany in the eyes of the world (Eg. international awards) and inspire others to taking up filming/acting?
After all that, you may conclude (based on your own opinions) whether or how much Leni's contribution, through her films, was more of an endorsement of Nazi ideals (Hence propaganda upon the German cultural/ social life), or promoting artistic Expressionism. A nice conclusion in the end would also be to say that regardless of her intentions, her films did have a significant impact on both the German people and the prevailing history, and that other contributing factors transformed German way of life, such as Hitler, etc.
Good luck, just my idea of how to approach this essay
