Unfortunately you just have to let her go with out pushing anything. In a perfect M she would be asking you to go with her and telling you all the details. But like must of use on here we are in bad M and just have to accept them they way they are because if you push the subject it will only make it worse.
I am with you because my W told me last month that she was going away for a weekend with the girls but then she never went. I knew it was not the girls because I know some of them. I just had to bite my lip and say have fun. It is very hard to do but over time it becomes easier. I still get a little emotional when I know she is lying to me but not nearly as bad as before. I just mentally prepare myself to let it go.
Good idea on the fiances. On the D thing I would not bring it up unless you are willing to hear that she wants a divorce. Because that is an option. Do not ask a question that you are not willing to hear what you do not want to hear.
Love is a decision. Genuine love is honor put into action, regardless of the cost.
Me:43 W:41 M:21 SS:25 S:19 D:18 BD1:3/16 BD2:10/16 W moves out 10/2/16