She may not have been unfaithful, but she is putting her professional license at risk, as well as her marriage. To communicate with ex-patients on social networks puts her at risk for accusations of dual-relationships, an ethical violation.
Because she is a counselor and can easily turn this back on you as if it is your problem,not hers, I strongly suggest that you find a very experienced, older therapist and get into couples counseling. You need to find someone who will not accept your wife's pseudo-explanations at face value.
Her behavior is inappropriate on a professional level, and dishonest at the personal level. You are right to be concerned, but you'll need professional help to sort through this. Counselors are often quite good at identifying other's weaknesses and excuses, and more often quite poor at recognizing their own shortcomings.