[William Cloud Hicklin]

Certainly Arwen was legally under a ban, not unlike that which had applied to her grandmother but of course for very different reasons. No elvish ship would have permitted her to board; and even had a ship of Men somehow found the Straight Road, she would not have been admitted. Her Aman visa had been cancelled.

The 'official witness' for legalistic purposes would likely have been Gandalf, whom Tolkien described as the plentipotentiary of the Valar in the context of Frodo. At what point was Arwen's "choice" deemed to have become effective? Either upon her marriage, or perhaps in a definitive statement to Gandalf as Manwe's temporary viceregent, I would venture.

But this of course implies nothing about some alteration to her body,* her hroa, which was of the Elvenkind, and thus immune to aging and sickness. One could I suppose imagine an "Oops-Arwen" lingering in Midle-earth for centuries, unable to sail West and unwilling to die, perhaps akin to the 'monsters' of Aman Tolkien posits. But instead she dies of her own (reluctant) free will.

*The movies' "Arwen is dying" rubbish, besides being nonsensical, is the most glaring evidence that PBJ never understood the book they were trying to adapt.