All that can presently (September 2022) be gleaned about
Cora Duncan from sheet music covers and by Internet searching is that she was presumably an English music hall performer who has been featured on on just one work namely
Only a Clown (1898) words & music by
Felix McGlennon, and published by
Francis, Day & Hunter, London W.C.2, England
From a poster, she is known to have appeared at the Argyle Theatre of Varieties, Birkenhead an 31st May 1897 and was descibed as a "Serio Comedienne and Burlesque Dancer".
Surfers are welcome to contribute any further information about this performer.