Yes ballads work on many levels and their effects are different for differnet audiences, but as your own example testifies they certainly work on the 'moral' level.
I happen to believe that the 'Cruel Mother' broadside is the original and certainly an important purpose here was to warn young girls of the nobility to avoid liaisons with servants. Child was wrong to identify Child 20 with European counterparts. The counterparts he quotes are actually relatives of C21. The few versions found in Denmark in the 19thc are most likely derived from Grundtvig's translations of British versions.