[Lalwendë]

I suppose there could be two ways of looking at Arwen's choice. Firstly, we could say that her choice to be mortal or Elven was linked to whether or not she wished to remain in Middle-earth. Arwen and her brothers were in a unique position as children of Elrond, who had been half-Elven and who had already made his decision. Part of the decision he made also involved accepting that as an Elf his 'natural' home would be the Undying Lands and accepting that one day he would go there. So we might say that Arwen's decision hung on whether or not she wished to go to the Undying Lands. Of course if she did, then after Aragorn's death they would be forever parted until the end of the world.

Or we could also look at it through Tolkien's ideals about marriage as a binding sacrament. Once Arwen had consummated her marriage to Aragorn would she be bound to him and therefore mortal? This seems like the most straightforward answer but then it raises questions of how the relationship betwen her hroa and fea could be altered by such a choice as that would be to fundamentally alter her nature.

Also why did she linger on if she had become mortal by marrying Aragorn? As I've said, she was not of Numenorean blood so presumably she did not have the same 'gift' which Aragorn possessed of being able to choose the moment of death. Wouldn't she age as any ordinary mortal woman might? This suggests to me that either she was 'gifted' herself with that choice. Would such a thing be permissible?