Your title asks whether she wrote anything after her period in Spain, but in the question body you wrote "during or after", so the answer then is probably yes, but the survival of any such writings is unsure.
In this piece about her life, written by the president of the Alumni Association at her former Oxford college, we learn that she was not only "in the office of" John McNair, but also seemingly helping to produce the ILP newsletter, then called New Leader:
Eileen followed Orwell to Barcelona in February 1937, and with her professional skills became the secretary to John McNair, the ILP’s representative, producing the ILP newsletter.
This doesn't exactly say if she wrote any of the content for the New Leader, or if McNair wrote and she was just his assistant, but I interpreted it as the former. (An amusing side note though not a reliable source: this is borne out by a very surprising source, the Doctor Who Wikia. Apparently a prose adventure of the Eighth Doctor featured George Orwell during his time fighting in the Spanish Civil War.)
She was volunteering for the ILP in Spain between 17 February 1937 and June 1937, so any New Leader issues that she contributed to wouldn't be included in this collection.
This collection of Eileen Blair papers at University College London might have something relevant: it includes some correspondence with comrades in Spain in the 1930s, as well as "miscellaneous notes and typescripts" both from the 1920s and "undated". However, they don't seem to have been uploaded as electronic versions.
It's also worth noting that the degree of her influence on the writings of her husband is unknown. Perhaps even in Homage to Catalonia you're seeing something from her, just not under her name. From the same Oxford college source quoted above:
There is disagreement between critics not only about the extent of Eileen’s influence on Orwell’s writing but on whether he selfishly demanded her self-sacrifice or she willingly gave it to nurture his genius. One of Orwell’s earliest biographers icily dismissed the notion that Eileen could have had any influence including on Nineteen eighty-four. Others discern more zest, colour and humanity in Keep the Aspidistra Flying and The Road to Wigan Pier completed after they met, than in his earlier works.
Certainly, A Homage to Catalonia reflected the experiences they had both shared in civil war Spain, and Coming Up For Air and Animal Farm were written during the height of their marriage. Orwell, in common with many writers, may have bounced ideas off other friends and contacts, including his various mistresses. However, it seems implausible that with Eileen sharing his experiences; typing and proof-reading his manuscripts; pulling strings to get him published and generally organising his life, he would not have been influenced by her views and suggestions. She was after all a highly-educated and opinionated woman with a good Oxford degree in English Language and Literature, and an expressive flair.
