I didn't know Joan, nor had I ever heard her sing (I live in Oz), but the news comes from my most favouritist online blog "Spitalfields Life" where one can while away many enjoyable hours in amongst the stories and photos of East End London folks and their lives and their history, as described by "The Gentle Author" :
https://spitalfieldslife.com/
There are a couple of stories on the site about Joan (described as a "Ballad Singer" - though perhaps not in the traditional folk / Child ballads meaning).

Not sure how I came across this site (it was some years back now), except that my great great grandfather, Willy Thacker, was an East Ender (before he was transported!!), so it may have been via a photograph of a district or a church or such.

ANYWAY, if you are not familiar with it, I hope you find much enjoyment there too!! (I know some 'Catters will enjoy the animal stories from Spitalfields and surrounds, as much as me!)

Cheers!
Rich-Joy
(Down Under)

PS    Mods, not sure if this is for Below the Line???