Supervising Sleep with Co-Worker

[BusyJD]

My Supervisor has been having an affair with one of my co-workers. (Someone she directly supervises.) This has had an affect on me and several other people in the office. The Supervisor is in charge of doling out work and gives her boyfriend the better cases. She also works on almost every case with her boyfriend. Its a relationship that makes everyone in the office uncomfortable. For me personally, I have been passed over for her boyfriend. This has had a lingering effect on my career. The way she treated me, I feel, is one of the reasons I did not get a promotion. Had I been treated fairly, I would have gotten more serious cases and been eligible for the promotion.

Is there anything I can legally do about this situation. (I do criminal defense work and no nothing about employment law.)