I think that Finrod's visit to an elderly Andreth is the necessary coda to Aegnor and Andreth's love story. Aegnor won't visit her, obviously, but Finrod would, and we can make use of that. But...we probably don't want to include the messianic hope of an incarnate Eru in our telling of the story. Not just because it skirts dangerously close to an explicit (rather than implicit) inclusion of the Christian religion, but because we are never going to do anything with it. The birth of Jesus would be well after the 4th Age (obviously), so any messianic foretelling we're getting has to point to Earendil, not Christ.
So, without that piece, what can they say to one another? They can discuss the limited immortality of Elves, and how the fate of Men is a giant unknown ('beyond the circles of the world'). That would be on topic, and the audience would care about that because it answers some of their questions about what happens when an immortal elf dies, and how that is different from when humans die. They can talk about amdir and estel. And they can talk about why Aegnor did not marry Andreth, and why she still wishes he had.
The big question is how much we would want Andreth to say about the fall of Men? We again don't want it to sound too much like the Garden of Eden story, but we also have to at some point have someone say or in some way let the audience know that Morgoth and/or Sauron were out in the East corrupting the newborn Men and so Men are fundamentally different from Elves and fear death in a way that they should not have done.