Very good question Post. Quite difficult to say as very much depends on the circs.
For example, if the OW did not know the person was married, maybe she could make the decision to not continue the affair, ask the cheater to conclude his current r'ship and then perhaps continue.
If the OW knew the person was married, decided to continue, and then received an email from an obviously hurt woman, she could perhaps respond - with compassion if she feels it, without rudeness if she doesn't?
I don't necessarily think she can do anything to cover over the hurt caused entirely.
I am also not 100% sure that I personally would seek an apology.
I guess the the point I have been trying to argue all along is that the OP, after much consideration, decided to seek an apology. She then received one, which she found healing/beneficial in some way.
Then you and other posters come on and basically piss on her, ranging from Tick tock saying she is a "bit of a twit" etc and then you now saying "a lot of people think marriage is outdated" blah blah.
I guess I don't understand why, when someone is clearly hurt, you feel the need to come and heap, to quote your phrase "more coals" on their hurt.
The OP never prescribed this method for anyone else, she merely detailed something that had worked for her. Then all you lot, come on her thread, and start saying how it's so mean that the OW is excluded from the sisterhood. I find it repulsive. You are entitled to your views, but if you are about common decency, is this the thread to share them on?