The one question that I have from your post is this, can my W respect me when I am NOT taking the hard line approach re OM? When I just don't say anything about it at all? I'm pretty sure she knows that I don't approve just from how I initially reacted.
There is a time for everything. As it's been said before, no one size fits all. The two of you are S, so she will not respect you sticking your nose in her business (as she'll see it) and telling her to choose between you & OM. She has already made a statement by walking away. Even though the two of you are legally M, she won't think you have a right to tell her anything.
Then there's the other thing that we've already discussed, and that's your female friendships that will need to die a sudden death.....and not be resurrected. To her, you were doing the same thing, just not a PA. So, she's got to have time to get over this dude and to see your changes.
That gives both of you time. Make time your friend instead of your enemy! Every time she sees you, make her heart flutter and wish she was back with you instead of the OM.
THEN, when she makes her little hint of wondering if the two of you could ever make a go of it......THAT IS THE TIME to tell her that the only way a M will work is for there to be no third parties involved.....not for her....and not for you.
