I finally found the information and found time to type it in. here it is, from

MOFFATT, ALFRED "The Scottish Song Book for Baritone: A Collection of the Favourite Songs and Ballads of the North" (London & Glasgow, Bailey & Ferguson, 1905) ________________________________________________________

A few years before her death, Lady John Scott supplied the present writer with some interesting information regarding her immortal song.

"Lady John Scott presents her compliments to Mr. Alfred Moffatt and begs to say ... she composed the tune of "Annie Laurie" and altered the second verse and composed the third verse. Allan Cunningham originally wrote the words"

Here we have the whole truth of the matter in half a dozen words. Again, in a letter to Lord Napier (I quote from Mr Davidson Cook's charming article in The Bookman entitled "Bonnie Annie Laurie: The Centenary of a Famous Song") Lady John Scott writes

"I must tell you the words of Annie Laurie are by Allan Cunningham, not by Douglas of Fingland. I daresay they were what he imagined Fingland would have written"

Allan Cunningham was a notorious forger and faker of old songs. William Motherwell has described his methods as a "wholesale mode of hacking and hewing, and breaking the joints of ancient and traditional song". Evidently acquainted with the old traditional lines [of an old ballad called "Doune sat the shepherd swain", preserved in the celebrated Percy Folio Manuscript, written about 1649

Faire shee was (of) comely hew,
Her bosom like a swan,
Back shee had of bending yew,
Her wast was but a span.

and also in some of the early printed-song books :-

I'm backit like a salmon,
I'm breastit like a swan,
My middle you may span. ]

he prefaced them with a pretty verse of his own making - one which introduced a pleasant sounding girl's name - and skilfully touched up the old verse. The completed "fake" must have fallen into Sharpe's hands as a genuine, ancient Scottish ballad. That Cunningham was quite pleased with his forgery is proved from his having reprinted it in his Songs of Scotland, published about a year later. This work is in four duodecimo volumes. It is full of impudent forgeries and faked verses. Its publication called forth the wrath of Motherwell, Laing, and other able writers of the period. In reprinting "Annie Laurie" Cunningham acknowledges Sharpe's Ballad Book. Possibly this was done in order to give the imposition greater appearance of genuineness. ________________________________________________________

I'll post links to the other Mudcat threads containing details of some of Cunningham's other exploits later. This bloke really fascinates me.

Cheers!
Ian