Moving forward together from a mess

[T1000]

But just like I thought would happen.

I think the what upsets me the most is a golden opportunity comes up like this to show me how serious she is about working on this marriage and she doesn't even hesitate. Stays the night anyways.

Something I'm learning right now. Don't expect anyone to share your standards. They are yours, hers are hers.
To you it's a golden opportunity to show how serious she is about working on the M.
To her it's a golden opportunity to enjoy herself with her friend, hopefully with your blessing because she doesn't want to upset you.

You say you knew it would happen. Does that mean you could have brought it up beforehand? It's not nice but in a way you set yourself up with an expectation that you knew deep down wouldn't be fulfilled.

Looking back with it being her friends birthday and you knew this would happen you could have told her how you felt but if she really wanted to stay over this time it would be OK.
You express how you feel, she hears you and is grateful of your trust and understanding.

Obviously it's easy for me to say that, sat here and not in your position.
Just something to think about.