Those who want a Bad Ending or as
mzer0 said Cathartic ending for Sophie it's never likely to happen. Because in media it's rarely done. Even in older movies like Tinto Brass All Ladies Do it, Monamour you'll see that the wife always gets to have fun and when they are feeling a little doubt (not guilty I must say) there's this one slut friend (like Amy) who will say, what she is doing is right and it's just physical and he should embrace it if he really loves her.
But the funny thing is when the FMC asks for advice because maybe the husband found out about the infidelity and left angrily the slut friend will be like "Is it another Women?" (implying if he is cheating) And after hearing her explanation will say "You got me worried I thought he is leaving you for another girl, don't worry husbands always comes back, you just have to lie or make him believe you truly love only him".
So it's always like the wife can cheat but the husband can't. And if he finds out about it, either he has to forgive, forget or accept that it's only a fling nothing more. And if he objects he is too old fashioned to cling to Morality, Faithfulness etc. And if the story is about husband cheating than almost always he gets a bad ending.
Even when a husband grows a spine and do something horrible he gets the most horrible ending (like the movie Unfaithful, Deep Water) though it's also somewhat bad for the wife but not much. I think movies like Unfaithful got hit because of their unusual ending.