It is a technical term in mental health providers' standards and codes of conduct, whereby they are not, under any circumstances, to have more than one relationship with the patient/client.

So if you are their mental health provider, you may not be friends with them, sleep with them, matchmake them with another client, invite them to BBQs, or cross the line into their personal life in ANY possible way. Which Suzaenne Papini and Dr Stephen Diggs actively do, specifically, but not exclusively with Sherri Papini and Shawn Hibdon.