She will be highly resistant to anything people (who are pro-marriage) will have to say to her. Even if you didn't suggest he talk to her, she will blame you. As I have told some others, the WAW finds the H as her easy target to blame with most everything. When her fantasy world starts to crack, she'll blame you. If she has problems with D14, she'll blame you. That's just the way it is.
In the past, has she talked about particular topics of resentment? Resentment seems to be a very common problem with WAW's. They carry this for a long time, sometimes years. Then it begins to affect their loving feelings. Sometimes the W starts to pull back sexually, and her H doesn't know why. It's b/c resentment has took a big toll on the attraction/desire for him. Resentment can show up in how she spoke to you (tone of voice, sarcastic, etc.). It is also a sign of losing respect.
Some women try to tell the H and he just doesn't get the message. By the time she no longer wants to share a M with him, she is done. She feels dead and empty....and blames him.
Needless to say, all those controlling behaviors you've shown must stop today. As soon as you accept that you have zero control over her, the better for you....and the better chance you'll have at a possible reconciliation. She is living a separated life from you, and does not have to give an account for what she does. Even if she was still under the same roof, you could not control her. Controlling actions are extremely damaging.
So, can you let go of this need to check on her, ask her questions about her personal life, drive by her house, etc.?
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!