This is not my discovery, a veteran RMIMers, Urzung (from Pakistan) mentioned this about 15 years ago. Finally getting the chance to use this info in the latest book by Sheo Khetan. She is in the Omar Khayyam drama scene (Khazanchi, 1941) singing the song 'peene ke din aaye piye jaa'
Please revise your filmographies of Munawwar Sultana (the actress, not the singer, they are different), if needed.
Now You Know!