No, she knew about it all before the marriage. It was a career move for MG. She had a another divorce and committed suicide like EH
She was also part of the adultery as EH was then married to PP with 2 kids and I think she was PP friend prior.
Pre Marriage. Martha was no dummy but she sold herself short. Clearly she knew about EH's demons, yet she married him as a career move. She was also friends with that lesbo commie Eleanor Roosevelt.
She, for her part, wrote fiercely to her mother: ‘A man must be a very great genius to make up for being such a loathsome human being.’
When Hemingway finally came to let her out he explained that he had done it for her own safety, but she was furious. Later, she wrote, “I should have known at that moment what doom was.”
It didn’t, however, stop her from starting an affair. She didn’t love Hemingway, she claimed, and she wasn’t physically attracted to him, but she admired him and was grateful for his companionship and leadership amid a horrific war. Hemingway regarded himself — and was mostly regarded by others — as the foremost foreign journalist in Spain, and was able to procure supplies, including petrol, where no one else could.
Known for being a bully at times, Hemingway was capable of subjecting Gellhorn to torrents of abuse: she described one evening as “a really excellent show but the kind of show usually reserved for enemies.”
Hemingway had started work on a play called The Fifth Column, based largely on his experiences in Spain and including a not-entirely flattering portrait of Martha as Dorothy Bridges, the heroine, whose main feature was her legs and who had “men, affairs, abortions, ambitions.”
By the end of 1938, Hemingway was back in Key West, trying to adapt back into family life with Pauline, but it was evident to visitors that he was unhappy. His brother Leicester noted that he was drinking an average of fifteen Scotch and sodas each day. He eventually retreated to one of his favorite islands, Cuba, to write, and Gellhorn joined him in the early spring of 1939.
Gellhorn wore a diamond and sapphire ring she described as “snappy as hell.” Although she had some doubts about marriage (upsetting Hemingway, who wrote that she had given him a “good sound busted heart”) photos from this time show them both happy, windswept, and smiling.
On November 21, 1940 they were married in the dining room of the Union Pacific Railroad in Cheyenne, Wyoming. Several newspapers covered the wedding, with one reporter describing it as a union “of flint and steel,” though which one of them was which was never made clear.
https://www.literaryladiesguide.com/literary-musings/marriage-of-martha-gellhorn-ernest-hemingway/