There's all kinds of background discussions going on about this issue right now, needless to say.
Most of those discussions have started with somebody firing a query to Hospital Administration that goes "I assume she was being understandably sarcastic about the additional three hours, right? I can't infer back what she meant in terms of her actual stamina constraints past the humor" and Hospital Administration firing back "No Merrin was being perfectly serious and did not mistake this for a joking situation."
The second-rank Keeper brought on site as Merrin's backup has by now been set up with a sim room hastily reprogrammed to mirror what Merrin is getting. Since the prediction market blanked he has resumed trying to shadow Merrin's responses to those, albeit with some irretrievable latency from extra steps in mirroring the output.
After watching them both for a minute, the consensus is that Merrin is still doing at least as well as the Keeper would. Possibly due to Merrin having roughly twenty as much emergency medical sim wall-clock time; possibly due to Merrin having tracked every aspect of this patient for the previous three hours. Without, apparently, her getting tired.
The other experts on this issue have not actually been trying to read off everything that Merrin has seen over the last three hours. Even the second-rank Keeper who specializes in attention-splitting hasn't been doing that, because then he'd already be tired by now. Keepers can decide to proceed past being tired, they can even decide not to be unhappy about that or distracted by that, but they can't decide to not have their reaction times degrade with expended stamina.