[Lalwendë]

I don't know if Tolkien realised it, in fact I don't know if he even read it, but Beruthiel and her cats are very reminiscent of a character in Gormenghast, the fabulous Countess Groan, or Gertrude. She is renowned for her distaste for other people, and in contrast, for the love which she bestows on her white cats (and her birds, too). I think Flay or Steerpike at one point is suspicious that the cats are spies; Steerpike in fact exploits Gertrude's love for her cats in seeking to have Flay punished.

I often wonder if the tale was left as a footnote as Tolkien had read Gormenghast and decided to shelve the idea?

I can well imagine that Gondor and Minas Tirith in particular at the time of Beruthiel was awash with ritual and politics, just as Gormenghast is. Perhaps Beruthiel was not the only one who had spies. I like to think she got to land again and found some allies as she seems, from what little we know, to have been a cunning woman. Married to one of the Ship-Kings, I can imagine she was left alone for a great amount of time while he went sailing.