Arwen could have, although it would have been preposterous, to stretch her life out like the later numenorean kings did, to lengthen their lives. Now, of course arwen would not do that, but the fact she could......And Aragorn suggested she find a ship to the Havens, but 'No ship will bear me now,' or something to the extent. So even though i doubt Mandos would be happy to figure out what the heck is going on when arwen set anchor in Avallone, she gave up her life on her own, and couldve extended it. She would not have wanted to live a mortal life after aragorn died, in a land where nobody dwells. So she laid down her life, which sense i have not experianced death i can not say for sure who this happened. Was it by 'letting go,' or giving up the will to live, or by stopping her resistence to death? I dont know, and sense this is a death topic nobody can say for sure unless they died or something and can still post. I dont know how much farther this topic can get without guessing.
I think as far as PJ adding the 'fate tied to the ring' part, it would have left out aso much as afore mentioned. Maybe elrond was just stating the obvious, that a victory by Sauron would ensure the death of many elves. <-------From Encyclopedia of Arda, On the Movies, RotK
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