Thanks, #. I see that the 1860 text already appeared there.

The 1855-58 date is probably accurate.

An account linking an American version to an supposed actual murder appeared in Frank Cowan's pioneering "Southwestern Pennsylvania in Song and Story 1878). Cowan's version involves not a lord but a lout, and the "Lily" gets a full name and a soiled reputation:

"The following song belongs to the era of the keelboatmen on the Ohio river and its tributaries, although it is sung occasionally at this day. The heroine is said to have been the daughter of a clergyman of Lexington, Kentucky - her name, Mary Morrison, on account of her great beauty and accomplishments styled 'The Belle of Lexington' and 'The Lily of the West.' For some unknown cause, she ran away from her home, and abandoned herself to a life of dissipation in Louisville. Here, a young man of fine address, from Ohio, became enamored of her charms and made a proposal of marriage to her. She accepted him. But while awaiting the wedding-day, he became aware of her shameless life; and in a moment of passion, incident upon meeting her in company with her lover for the nonce, he killed him: for which he was tried for murder and convicted; and while in prison awaiting the day of execution, he composed the song which bears her name.

"For all of which, and the song, I am indebted to my genial friend Wm. H. Morrow, Esq., of Manor."

My take on all this, even before finding this passage, was that the only sort of woman in the Victorian Age to have a public nickname like the "Lily of the West" would have to be either an actress (like "The Jersey Lily,' Lily Langtry), or a prostitute. Indeed, actresses in general were often assumed to have been scandalously free in their relationships - like chorus girls in the early 20th century.

I believe that angle would not have been lost on many 19th century readers, audiences, singers, or reciters.