^^^ A young lass said to me
My mother won't mind
And my father won't slight you
For your lack of kind
Then she laid her hand on me
And this she did say
Oh it will not be long love
'Til our wedding day

Then she went away from me
And she moved through the fair
So fondly I watched her
Move here and move there
And then she went homeward
With one star awake
As the swan in the evening
Moves over the lake

All the neighbours were saying
That the two would ne'er wed
For one had a sorrow
That never was said
And she smiled as she passed
With her goods and her gear
And that was the last
That I saw of my dear

Last night she came to me
My fond love came in
And she moved so soft
That her feet made no din
And she lay down beside me
And this she did say
Oh it will not be long love
'Til our wedding day

The song is about Tuberculosis which, at the time it was written, bore the same stigma as aids.
In the first verse she passes the disease to her lover "Then she laid her hand on me"
The second is simply a lover's verse.
In the third she is taken away to a sanitarium where she dies. While the neighbours gossip, they dear dare not speak of her illness by name... "one had a sorrow that never was said" Much the same way as "Cancer" was always said in a whisper, when I was a child.
In the final verse he sees her, either in his delirium or as a spirit
"And she moved so soft that her feet made no din" And now she tells him that soon he will join her "And she lay down beside me and this she did say, Oh it will not be long love 'Til our wedding day"