Why does nobody think its fishy that she put on a maid costume and went to mop his room
It's in the chapter, in case you forgot from the previous chapters, she lost a bet on the soul pact that forces her to go clean every day or she dies, I forget the exact terms of the deal.
On another note, Frey somehow never realized that Irina gave him the second stack until the end of this arc in the novel, which was really dumb and easily one of the worst parts of the early story, so it was nice to see them change it.