The answer appears in Tolkien's The Road Goes Ever On
"The question Sí man i yulma nin enquantuva? and the question at the end end of her song (Vol. I, p. 389), What ship would bear me ever back across across so wide a Sea?, refer to the special position of Galadriel.
She wasShe was the last survivor of the princes and queens who had led the revolting revolting Noldor to exile in Middle-earth. After the overthrow of Morgoth Morgoth at the end of the First Age a ban was set upon her return, and she she had replied proudly that she had no wish to do so. She passed over the the Mountains of Ered Luin with her husband Celeborn (one of the Sindar Sindar) and went to Eregion.
ButBut it was impossible for one of the High High-Elves to overcome the yearning for the Sea, and the longing to pass pass over it again to the land of their former bliss. She was now burdened burdened with this desire.
InIn the event, after the fall of Sauron, in reward reward for all that she had done to oppose him, but above all for her rejection rejection of the Ring when it came within her power, the ban was lifted lifted, and she returned over the Sea, as is told at the end of The Lord Lord of the Rings."
JRRT, The Road Goes Ever OnThe Road Goes Ever On, 1967
So while a lot of posthumously published material exists about Galadriel, this is the explanation that Tolkien himself chose to reveal to readers, published in 1967.