I found it!
But
Ulmo answered:
"Nonetheless Miriel died. (.....) And death is for the eldar an evil, that is a thing unnatural in Arda Unmarred, which must proceed therefore from the marring. For if the death of Miriel was otherwise , and came from beyond Arda it would not bring grief or doubt."
"unnatural" was a big clue! I knew then it must be about death. (If it had been in a fanfic, however, I would have suspected something quiiite different.
)