My wife recently quit a job where the supervisor had a sexual relationship with her co-worker and made a sexual advance towards my wife.

I do not see a question.  However, if you are asking if your wife has a claim, the answer is maybe.  Sexual harassment in Tennessee must be pervasive or severe.  In general, severe isi something similar to rape or sexual assualt.  That means that most sexual harassment claims are brought pursuant to the pervasive standard meaning that the sexual conduct (statements, actions) must occur repeatedly over time.   A single comment or action (or advance) is not enough.  Now, her co-worker might have a sexual harassment claim if the relationship was forced.