Your post says so many things about you.
Clearly you are not in a forgiving state and need counseling - individual and marriage.
You blame the OW. You squarely put it at her feet - your language (she tried to kiss him, she tried to get him to go out, her husband doesn't know the details). You clearly think that she should suffer in some way and be punished and be miserable - like you.
It kills you that perhaps she's not. That somehow she came into your lives, created this chaos and upheaval and shoved off without a hint of remorse or having to get any payback.
OH WELL.
Maybe she's all the things you think. Could be true. Probably fairer to say that your husband is equally guilty and accountable. Either way - her relationship with her husband is not any of your business. And if she's no longer messing with your DH than you really shouldn't be focused on the details of her at all. If your husband was weak and ready and cheat - it would have been some other regular contact - co-worker, babysitter, 7/11 worker. Who knows? You're obsessed about the wrong thing. Get over her. It's pathetic and makes you look pathetic. You going to her DH will make you appear deranged and sad.
Get your shit together. Ask for a trial separation if you have to. Good grief - have some self-respect about yourself. Decide if you can look at your husband after he engaged in an almost kiss and long hugs.