She's a STUPID BITCH, forget her
I'm so sorry for your pain, it's HORRIBLE that you are having to go through this.
Ughh I just want to scream so I am writing you. Again, I don't know if I will send it. The ghost of a friend I used to have. Friend 1 and and Friend 2 were just in my store. Friend1 said she waited til you left to come in here. I hate this. Nothing can be done, too uncomfortable for everyone. It just sucks. We can't control people, we can't change the past. Friendships around here will never be the same.
To find peace, you will need to work on detaching. The most effective way to do this is NC.
NC = no new hurts.
Keep that letter to yourself. Write it on toilet paper and flush it down the toilet. You will get the feelings out without giving HER the satisfaction of knowing she is getting to you.
It is so hard, truly I know.
Focus on you. Do you have a GOOD IC? One that not only listens but gives coping strategies? Helps you grow away from your issues and towards loving yourself enough to be able to say "Enough?"
I tell you what, the healthier I have gotten the easier it is to look at your H's behaviors and know what's crap and you don't have to accept. It's made me strong enough to decide he can catch up or get left the hell behind.
I think if you could get there, OW wouldn't be the issue she is. That's not saying she shouldn't be an issue at all, but some of her emotional power over you will wane when you grow in yourself and away from expecting anything from two obviously selfish people.