Right decision. If things go south in her marriage, you won’t be the reason, but she will remember you as the guy with integrity who also shared crazy chemistry with her and not the guy she cheated on her husband with. When a marriage goes south, and adultery played a part, the next relationship almost never ends up being with the subject of the adultery.
Too much guilt. Ask someone who knows.
She won’t forget you, I promise. And if the opportunity arises for an honest thing between you, it won’t be clouded by a dishonest one.
You know. Can’t unpickle a pickle.