Snowdrop, I wrote a couple of letters to my WH's AP. She works at the same place both me and my WH work. the balls of that woman for having an A with a married man in such close proximity.
I also confronted her face to face, ran into her by chance at work a few times. For months, before running into her, I obsessed about what I would say to her. I didn't want to come off crazy and trashy but just like you, I wanted her to know what I thought of her. I also went to her boss and ratted her out, only after i found out they were still lying to me about certain details. a lot of people found out about it at work, not from me, but that part to me is a double-edged sword. on one hand I am glad her reputation went down the gutter, but it also put my marriage on display.
I would be lying if i told you confronting her and sending those emails didn't feel good, however, that feeling didn't last long. it was a band aid for my anger in that moment. I thought it would give me some kind of closure or satisfaction but in the end, it really didn't do me much good. It's not going to help with the healing process. If anything, it could do more damage to you, depending on her reaction. Lucky for me, this poor excuse for a woman was so worried about losing her job, she was very apologetic and very accommodating but even that wasn't helpful to me. the pain was and is still there. not as bad as it used to be but only time, IC and a lot of selfcare helped me get to where I am today, not confronting that piece of garbage.
on a side note, I respectfully disagree with people who say the AP should not be blamed or that it is misplaced anger. The AP absolutely is to blame for their part. These people knowingly get involved with someone who already has commitments toward someone else. as human beings, don't we owe each other respect and consideration by not getting involved with someone else's spouse?
take care of yourself, much love and warm wishes to you!