I've been singing The Wife at Usher's Well off and on for over 30 years. We just recorded it but I can't remember where I learnt the songs nor can we find any lyrics that match up.
Here are the words for my version:

WIFE AT USHER'S WELL

There was a knight and a lady bright
Three little babes had she
She sent them away to the north country
For to learn their grammerie

They hadn't been gone but a very short time
'Bout six months and a day
When death, cruel death, came riding along
And carried those babes away

And when she heard her babes were dead
She did mourn, she did weep
'Till they came to her one dark midnight
Crying, "Mother, we cannot sleep"

She set the table, she gave them wine
Gave them bread and gave them meat
But they were not able to touch a bite
"We are dead; we cannot eat

"Mother, oh mother, we cannot stay
We must leave ere break of dawn
Your weeping keeps us from our rest
In our graves where we belong"