I don't think the tune of "Frankie and Johnny" (at least the one I am familiar with) quite fits the Ballad of Helen Titchener, as the verses are basically 6 lines:

Frankie and Johnny were Lovers
Lordy how they could Love
They swore to be true to each other
Just as true as the Stars above
He was her man
He wouldn't do her wrong

I always liked the last verse:

This story has no moral
This strory has no end
This story only goes to show
That there ain't no good in Men
He was her man
But he done her wrong!

To make the tune of F and J fit the Ballad of Helen Titchener, you would need to add another 2 lines to each verse of the latter (basically a chorus); it could be "She stabbed her man, 'cos he done her wrong"

Can I have one third of any royalties?