Ah, the exit to that level is in a weird spot. All you need to do is touch a big terminal in one of the rooms in the floor with all the shotgun dudes, and then make your way to that big cafeteria room with the LMG. When you're there, the exit should be a 2nd set of stairs that's to the left of the kitchen, directly perpendicular to the stairs you took to beat the 2nd half of the level. hope this helps!
If I may add one more addendum on Achira, I tested her after finishing my review and it IS possible for her to kill you (on my version of the game at least). The problem is that it takes her around a full minute to actually kill you because she relies on making you fat instead of a separate kill timer, which may make her more threatening if you have been attacked by Milkamean or Suki, but on her own she's kinda useless. While I am glad they made her more of a threat in a newer version of the game, it is sad to see that intentionally letting her into the office to save on power has been nerfed, because that probably was the main reason why I won potluck
