I wouldn't go with her to the reunion. I would tell her "W, I am not interested in pretending to be a happily married couple just for the sake of appearances." Then politely thank her for the invite and do something else that night.
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.