The entire show is build on Mieko being a tool for negotiation. She was even implied to have an intercourse with one of the 'client'. The only thing different in this chapter is that Mieko is drunk. Some people can be a lot more honest when they're drunk (I say some, not all people), Mieko in this case start to be a lot less careless and disregard her position as a tool for negotiation. It's even implied Mieko only has romantic interest towards Section Chief in this chapter. In a way, this is indeed rape, but if she was still conscious in bed, she would've probably accept the president's embrace and take this as just another part of her Job. Honestly, the story progressing in this direction isn't that much of a surprise, Mieko doesn't seem like the type to crave man for mere sexual relieve, neither is she interested in the money, so she must be staying for a personal reason. It just so happen such personal reason, is a romantic interest toward the Section Chief.