Alas, Anarion, yes, Goldberry is one of those characters who seems simply to disappear off the radar after Frodo has his first experience of adoration with her. It was a sort of mini-revelation, though, I guess, and in her house Frodo does dream of the sea. Well, I guess she also gets to name him "elf-friend".
Still, a Persephone who is not in thrall to the Underworld raises all kinds of possibilities...
Bethberry
PS. Yes, I know, very tardy reply. The orcs of real life have that tendency to keep us away from middle-earth.