The key here is self-respect. What I mean by that is not accepting W's sloppy seconds and not making it too easy for her to reconcile. You are a quality person.
You REALLY have the upper hand here. Not W. Not the OW.
For me, what self-respect means that I will not be a second fiddle to anyone. Self-respect means zero drama. All of that chit about getting hot and cold is manipulative. No two ways about this.
I am a lot further along on the path than you are and I now recognize it. I am absolutely fearless and I would not be shy about laying down conditions.
If I were you, I'd hear what she has to say then go with this:
I can see that all of this is a very difficult and painful experience. It has impacted me too and I do not feel safe with you. Trust needs to be earned here. Your actions are not trustworthy.
In order for ME to consider reconciliation, if that ever happens, I require the following from you in order to feel safe again:
1-OW needs to be completely out of the picture 2-No contact with OW in any manner even if it is work-related 3-Write a no-contact letter/email to OW to be reviewed by you and approved by you prior to sending to OW 4-We continue living separately 5-Counseling is non-negotiable 6-We are not going to be involved or start dating for a while until all of the conditions are met and followed through
Tell W that you value yourself too much to be put in this position ever again and you are now aware of your needs. You need a partner who is supportive, open to having difficult discussions if there are ANY problems whether it be large or small, not run away from problems, and thinks you're the bee's knees.
Then wrap it up by saying that W has some decisions to make here and it is all on her to clean up her mess. You cannot help her nor will fix it for her. It is W's responsibility to fix this mess.
I'll smack you, NYG, if you say "I miss you, I love you" or some other sappy sentiments to W. Time to grow a backbone and lay it all out for W.
