Salem, Thanks for the photo. A glamorous-looking lady! And fairly clearly the same one as referred to above by suttontrust as being Nora in the Gay Parisiennne. It increasingly looks as if I have been on the wrong track, but I am asking my wife's cousins if they can come up with more evidence of their grandmother having been on stage.
I have a scan of a pretty programme from the Palace of Varieties. The programme was a piece of card folded into three columns, and Edith Courtney is listed as a ballad singer at item 10. See attachments. It seems likely she is 'yours', though I still have faint hopes that my Edith was somewhere on stage.
I have some Word notes 'an' Edith Courtney's performances, as well as quite a few some scans of reviews of performances she was in (though she is not mentioned personally) and other images. If you are interested, please send me your email address via a RootsChat personal message.