Ya'll stop grasping at straws. They don't have the emotional attachment to each other that they once had (i.e. no more banging). I can't figure out what kind of relationship they have (sleeping together w/o touching, then she moves to the couch, then back in the bed). As long as Maya has BT (Boy-Toy) to help 'release' whatever tension she has, there isn't a chance that she would even have CASUAL sex w/ Stepan.
IMO, she likes sex better w/ BT then with Stepan. Not just because it is a new relationship. But she can manipulate (control) the sex to her liking (and BT is OK with that). Not that Stepan had much to say when the engaged in coitus, but you can tell Maya enjoys banging w/ BT).
Also, subconsciously Maya has lost respect for Stepan; evident that he tolerates (for the lack of a better word) their current living arrangement (she fucks another guy then comes back to the apartment and gets into bed platonically w/ a guy that accepts that she just FUCKED another guy and he's just like a shriveled up salami). Maya has the best of both worlds while Stepan is completely lost. I feel bad for him and Maya should "let him go". But as long as they live rent free,....