"If the *speaker* is a woman addressing her sweetheart Malcolm, the song becomes even more bitter, like some of Sassoon's Great War verses indicting women as encouragers of war."

Well there is quite a hint in the following:

Original verse:
"Will ye go to Flanders, my Mally-o,
Will ye go to Flanders, my Mally-o,
There WE'LL get wine and brandy,
Sack and sugar-candy,
Will ye go to Flanders, my Mally-o.

Modern additional verse:
"And will ye go tae Flanders my Mally-o
Tae see the bonnie sodjers there my Mally-o
They'll gie US pipes tae blaw
Coats o red an kilts sae braw
The finest o them a' my Mally-o

The song is about two young men, the singer has already decided to go and is trying to convince his friend "Mally" to join him.

Song even with modern additional verses has got nothing whatsoever to do with the First World War - anti-war song?? Nope all about the Army being a way by which the unemployed of those times could find food, clothing, pay and board and in which the young could find adventure and possible riches, very typical of the young to be lured by danger, they after all are invulnerable and if anything happens - it will only happen to somebody else.