Sandy made a cameo in Becoming Led Zeppelin, which I saw yesterday (highly recommended).
In a newspaper clipping from 1970, right next to an announcement about Zep, was a box that declared "Joni and Sandy" as the U.K.'s favorite girl singers.
The doc ends with a triumphant Royal Albert Hall appearance in 1970 with many of the group's family members in attendance. We didn't get anything past Led Zeppelin II. By stopping in 1970, they deftly avoided more controversial areas of the band's history.
As it's called 'Becoming Led Zeppelin' 1970 would be an appropriate place to end the movie.
'Deftly avoiding' anything probably didn't come into it.
What controversial areas are we talking about ?