How is it that it has been a year of H*LL and I still hurt over her?
I think you already must know the answer to this deep down. YOU are allowing yourself to continue being in hell indefinitely, and feel like your heart is being ripped out over and over again. Not only is that doing nothing to help your relationship at all, but it is killing YOU.
When you see her all the time, talk to her all the time, go to her house for your social hours...you will NEVER stop feeling the hurt over her. Finding confirmation of the PA? Emotionally devastating on a night you could have been spending time with some people who TRULY care about you, investing in yourself and one of YOUR dreams, the possibilities are endless, but instead you were doing the most self-damaging thing possible.
I'm sure you ARE amazing, and your W knows it. And she also thinks she can have it right alongside with AP. It simply can't go on. You are devaluing your own worth, which we just confirmed is very high, in both her eyes and yours. You cannot have heartfelt talks with her. She denied, denied, denied the PA even when directly confronted. Not until she had nowhere else to run, due to your proof, did she change her tune. This should be very telling for you. Your conversations are going nowhere and only take place to soothe your W and assure her that everything is still going according to her selfish, out of control plan.
You have told her you want space. STICK TO IT. You have the "ammo" now of just confirming the PA to justify why you want nothing to do with her. Not that you needed it, but I have been in your shoes and not known how to do a 180 out of nowhere when I have been friendly and suddenly try to close the door. You feel like you need an excuse. Well now you have one. Stay strong.