Relative Powers

[Thalion]

'Galadriel was the greatest of the Noldor, except Feanor maybe, though she was wiser than he, and her wisdom increased with the long years. (...) These two kinsfolk [Feanor and Galadriel], the greatest of the Eldar of Valinor, were unfriends for ever.'

What work does this come from? I'm not denying its authenticity, I just wasn't able to find it myself...

EDIT: NM, I found it in Unfinished Tales

HOWEVER...in reading the passage (and this is going to sound picky)...I wonder what Tolkien means by the word greatest...to me it seems possibly to imply fame or had the most dealings with others...almost like he's saying "Galadriel had the most renoun of the Noldor, except Feanor maybe, though she was wiser than he..."...not so much that she was the most commanding or had more power than others, just that because she stayed in Middle Earth so long and because she strove against the forces of evil so long, she invariably will appear to be "the greatest" or have lasted the longest or something along those lines......

...A reading of the word "great" in the OED (for which Tolkien himself was a writer) leads one to be able to draw this conclusion, although it necessarily allows one to see the word "greatest" in a more common meaning of implying more power or statur...I back this by saying that the essay to which the lines come from are characterized by Christopher Tolkien as a "very late and primarily philological essay..."