"All I know is, I'm extremely introspective, observant and nosey."
This may sound a little harsh, but you opened the door on this issue. The operative word, here is: nosey. What would be the positive benefit by ratting this person out? People make choices, every day, that are stupid, self-motivated, and thoughtless. Is this a shame? Of course, it is - but, we're flawed human beings and "allowed" to make dumb decisions. Is this something over which you believe you have some control? Absolutely not - the only person over which you have control is yourself, period. So what if this woman is paying more attention to her appearance? Is that a bad thing? Is there something that may be lacking in her personal life that may be causing her to make a stupid decision? Are you attempting to stand as judge and jury of another human being as if you haven't made dumb choices, yourself? So what if the boss-man in question attends church and has a wife and children? You have no business putting your nose in places that do not concern you, personally.
Sounds to me as if you're placing your focus on someone else's activities, rather than attending to your own business. This focus of yours will affect your ability to perform your job effectively and, eventually, begin to consume your personal life. Hence, you'll get some sort of "warning" or engage in some sort of discussion with this very person - who is YOUR boss - and, you'll harbor even more resentment against this person.......the thinking behind this might follow the lines of, "Well, he can get away with anything, where does he get off telling me that I'm not doing my job?" As long as his activities are not affecting you, personally, or affecting how the business is being run, it's none of your business. If, indeed, his activities begin affecting the business, it will all come out in the wash, and it is not your business to "blow the whistle" on anyone. As an aside, here, "blowing the whislte" on someone in a business/corporate environment has to do with how their decisions and choices affect the integrity of the business and the public, at large - NOT in reference to whether or not their choices offend you. As for it affecting you, personally, you also have choices: you can leave your positition and find another place of employment.
Nothing in this world is perfect - that includes workplaces, bosses, coworkers, spouses, etc. Mind your own business and attend to fulfilling your own job description and leave the judgement and vengeance to kharma. Otherwise, you would be engaging in a very nasty little pasttime of causing trouble for the sake of your own agenda. By the way, my spouse is friends with single women and I have absolutely no qualms about it, whatsoever - that's what comes from self-confidence and a relationship that is based upon trust, honesty, and respect.
Indeed, the legal term for such actions is called, "sexual harassment," and can carry extraordinary legal/civil ramifications. The original poster has only managed to provide hints and allegations of an affair that cannot be supported (document, document, document), and it's obvious, from the language in the posts, that the original poster is harboring jealousy, rage, and a baseless sense of vengeance in connection with the supervisor-in-question.