Even if there is not an affair, she is moving in directions distant from the marriage (you). An affair would just be another symptom of her dissatisfaction with the M. Either way, it is important for you to understand what she is looking for that she doesn't have in the M.
Try to piece it together by really reflecting on what she has told you. What are her consistent complaints? What about you has she criticized? What have y'all fought about? What do her 'new ways' indicate she is looking for now?
"What is best for my kids is best for me" Link to quotes: https://www.divorcebusting.com/forums/ubbthreads.php?ubb=showflat&Number=2879712