This documentary is very poorly made and presented. It begins with a distracting rambling of opinions by the 4 or so talking heads about the personal traits of the sisters their personalities and relationships that is frankly meaningless to the viewer without a background in their lives.
This information could have come out during the telling of their story but for the first 15 minutes you are left wondering what on earth is this about; it is obviously aimed and trying to draw you in, but if presented by just the narrator it might have been achievable, but the wide range of talking heads with various accents and various speech characteristics makes the whole thing so hard to follow. The narration is the only sensible thread through the who documentary and gives you a mooring into the story line, the talkings heads on the contrary are utter distractions and add no material to understanding the story.
Another factor is that archival footage is inserted to pad out the content and the film clips that sometimes are clearly not of the period and clips showing characters standing together , with backs towards the camera, the give the viewer absolutely no idea of who is in the photo and what the photo purports to infer. Indeed in the last few minutes there is a montage of archival clips, some repeated, but some pointless, for example ladies dancing in a 1920s speakeasy nightclub to what purpose this was included only the producer or director can tell us if we dare to ask.
Anyway, towards the end of the first 20 minutes or so you are starting to get the drift of what the storyline is and it is interesting, but once again it is very hard to grasp what the talking head is trying to say and this spoils what could have been a good documentary. Now I understand the need to sometimes interview people for a documentary but talking heads that offer opinion where the narrator would be more appropriate and better understood would result in a more enjoyable watching experience - which I would have thought would be precisely what you are attempting to achieve in a documentary otherwise why make it!