Is her ex seeing someone? I understand your feelings, but it seems like she's going back to seeing what it would be like to be a family again with her H.
It would help if you put your vitals in the signature line, but what ages are you and your W? It could be she's going through a MLC and she actually has felt guilty about "cheating" on her H all these years and didn't want to hurt you so she couldn't say 'no'.
All of this is speculation, but it just seems a little odd that she's been M to this man this whole time and you didn't say anything about it. Or did you? It almost seems like it was an escape door for her and that you were a second choice or else she would have closed the book on her R with her H.
M-43 W-40 2D - 9 and 5
Emotion, yet peace. Ignorance, yet knowledge. Passion, yet serenity. Chaos, yet harmony. Death, yet a new life.