Which Elf had it hardest?

[Rilwen Gamgee]

I would say Galadriel had it the hardest. She lived a long life and much of it was sorrowful. First of all, her brother, Finrod, died. Also, if I'm not mistaken, she traveled to and from Aman and Middle-earth twice, which is not an easy trip! Next, she bore a Ring for almost all of her life, which put stress on her to keep the land she was the Lady of safe. Her daughter, Celebrían, became overcome with grief, and sailed over the Sea; another family member was gone (however they would reunite after Galadriel returned to the Undying Lands). Next, there was the dilemma of Arwen and her choice of mortality. A quote from "FotR" also describes Galadriel's tragic life:

...a living vision of that which has already been left behind by the flowing streams of Time.

3 (or 2, not counting Celebrían) family members lost and the burden of being a Ring-bearer. Certainly not a life everyone would want.