Can Clinical Psychologists reveal that a person is a client to their partner?

Imagine a psychologist (Dr. P) is walking in a street with his wife. He sees one of his clients walking toward him. As she passes Dr. P, she smiles, waves hand, and then continues on.? Dr.P smiles at the client as well. His partner sees this and asks who the person is. How Should the psychologist respond? Do you think the fact that the client revealed that she is acquainted with Dr. P a justification for him to tell her the truth – that she is a client? Is there a way of avoiding this situation?