A friend and I were working on a mind map for this question in class today.
It's addressing the 'significance' part of the syllabus.
Interpret the quote first. Personally, I interpreted it as that the way Leni Riefenstahl helped create some of the most famous images of the Nazi party ultimately left the everlasting image of her being the Nazi cinematographer.
We mentioned her films 'Victory of Faith', 'Triumph of the Will' and 'Olympiad'. Although 'Victory' was kind of a fail it was still the beginning of her Nazi propaganda work and she continued on with it despite the fact that she always denied ever creating Nazi propaganda. Chuck in some examples like the possibility of her helping with the organisation of the Nuremburg rally in 'Triumph' (I believe Rother, the historian, said something about how it had the precision of a Hollywood musical... or someone did at least... maybe Bach. Just check that one out) and how even though 'Olympiad' is one of the most famous sports documentaries of all time there are still strong Nazi elements in the film (the salute, swastika, promotion of the perfecty Aryan race, etc.). Her involvement with the Nazi party and her decision to make these films for the Nazi party ultimately shaped that image of her being a Nazi cinematographer/propagandist.
Hope that helped a bit.