I'm a librarian who loves anime, manga, and reading a wide variety of genres.
Nils' ex-wife is one of the few characters in this book that really seems to have it together. Sure, she still sleeps with Nils, but I think their marriage might have ended because she realized that she preferred not being married (a guess on my part, since readers still haven't been told why they got divorced). I think she figured that Nils was happy as she was with their "friends with benefits" relationship - not taking the time to verbally confirm this with him is one of the areas where she went wrong. Other than that, she seems happy and successful, which is more than I can say for Nils.