Thanks TT, I quite agree.

Tolkien's reference to Mary Renault is quoted in the Letters:. He writes that he ‘was recently deeply engaged in the books of Mary Renault; especially the two about Theseus, The King Must Die [1958], and The Bull from the Sea [1962]’."

The phrase "deeply engaged" seems to point to a particularly close reading.

Another letter from the same year that has only been summarized has Tolkien, also in 1967, refusing another effort at biography of him (or what he calls his "interior literary history") saying he's too busy with the Silmarillion, but he adds the odd note: "he would like to know how author Mary Renault would answer the same question."

The most natural reading of this seems to me that Tolkien was aware of Renault being unable to engage in literary biography because of the lesbian theme.

An unsourced memory noted in a fan forum had Tolkien urging young Mary Renault, when on the cusp of being a published author, to avoid a male pseudonym, i.e. changing her gender for the public.

https://www.reddit.com/r/tolkienfans/comments/8xz53v/tolkien_and_mary_renault/