I checked the letters published in 'Letters' anyway, and unless I missed something Nerwen, I couldn't find anything there. A footnote to draft letter 297 notes that Galadriel's personal ban was lifted and: 'So at the end we see her taking ship'.
And this is the same footnote that perhaps confusingly notes that Galadriel wished or prayed (in her lament) that Frodo be granted a: '... sojourn in Eressea, the Solitary Isle in sight of Aman, though for her the way is closed.'
Which leaves one wondering if Tolkien meant that Galadriel was likewise going to Eressea in theory (after her ban was lifted), or if he simply used this phrasing without really meaning that this need be her only destination -- and at least with respect to a permanent one, if the other letter comes into play.
Of course that's a big if in any case, as this letter dates to 1967 while the Waldman letter dates to 1951. Did Tolkien somehow remind himself of what he had written so many years ago to Waldman? Seems unlikely, although it could be that the idea that the Exiles were not to dwell permanently in Valinor 'persisted' in his head, or was at least in play when he wrote this footnote...
... or not
Anyway I can't recall, at the moment at least, what this person might be referring to.
Back to the Waldman letter for a moment: 'They were not to dwell permanently in Valinor again, but in the Lonely Isle of Eressea within sight of the Blessed Realm.'...
... Valinor is not Eldamar, although admittedly the second half of this sentence appears to rule out Eldamar as well -- as Eressea is supposed to be where they will dwell, even if Eldamar is not mentioned -- so I'm not sure why I took the time to split that hair!