When I was young, my grandmother, from whom I got my interest in Wales and things Welsh, gave me a horse brass that pictured Jenny Jones. At the time I didn't know who Jenny Jones was (just that she was Welsh) and I still don't really know what a horse brass is (just that I had one). Perhaps Jenny Jones horse brasses are common and that is why they were discussing her on that pub's website. Anyway, later in life I saw Jenny Jones again in the form of Staffordshire china figurines of the 19th century. Here is what Kovel's has to say regarding the Jenny Jones of Staffordshire figurine fame:
"Jenny Jones was a dairymaid at Pontblyddin Farm. Her sweetheart, Edward Morgan, was a ploughman. Morgan spent 20 years with the navy and returned and married Jones. In 1825 actor Charles James Mathews met the Morgans and heard their story. He composed the 'Song of Jenny Jones and Ned Morgan,' which was used in a show in 1836. The romantic ditty was popular for the next 20 years. Figurines of Jenny Jones, Edward Morgan, and the pair leaning on a milestone were made in the 1840s."

I don't know if this is the same song as the one offered on the pub website, or indeed if Pontblyddin Farm is near Llangollen... but thought perhaps this might be of interest. Margaret