With respect for your knowledge and experience in some kind of therapeutic world, this is just not true. I've been professionally involved with many psychologist-psychiatric types at the higher ends of the therapeutic spectrum, read tons of hospitalization and therapist records, and it is quite common for professionals to meet with the family members of clients and to talk with the family members of clients, with the permission of the client. Information from sources outside the client can indeed be helpful to someone's therapy. To make such a sweeping statements that therapy is "supposed" to be any particular way is almost always going to be wrong, sans sexual activity and financial exploitation. I suspect your experience may be more limited, but it is absolutely okay for a therapist to get information from a client's family members (and it does seem to me from my own experience that "investigation" or detective work is very much a part of what goes on).

But I'm not going to get into some petty argument with you. The OP and anyone else can decide what they want to believe. I'm going to bow out of this thread and wish the OP the best. I hope you (the OP) will update us in the future if you want to and let us know how it goes.