"The Enemy Within":
Although it's not completely available at Trekcore, the scene with Fisher running to the intercom panel reveals the corridor outside Janice's cabin (the odd thing here is, that he must have left the briefing room set to get to the panel, notice the red alert light further down the wall but
opposite Janice's cabin door):
You're right, this is no longer cabin 3C 46 but 3F 125 and the yellow door is missing in the above shot. I concur this is a different cabin, but where?
It was Harry Mudd's cabin number in "Mudd's Women", but then the environmental ladder booth has been sealed by the time of "Charlie X".
Or it was on Main Deck 5 before Spock moved in ("Amok Time"), but then the entire corridor underwent a major refit.
I think I'll prefer she moved into Mudd's former cabin: