This has gotten way off tract, a new thread should have been started rather than hijacking this thread.
That being said here are a few facts:
Parents have just as much right to take a child to a psychologist as any other health provider, they don't need special permission to do so and if this is a professional counselor, they abide by the rules and laws related to that practice.
There are rules of confidentiality and different than medical as to what information is released to a parent, just because you are the parent doesn't give you the right to know every detail of therapy, you will be released information as allowed under the law.
As to the situation where the finacee provided medical insurance, that is wonderful, what a progressive employee benefit! It doesn't matter who's policy covers the child, only that the child is covered. That doesn't give the fiancee, parents or step-parent or you anymore access to the others medical records or confidential informaiton than any other situation. It doesn't entitle any of the parents to information beyond what is allowed by law. I'll bet what happened is that the new cards were not available yet, and the father, child and fiancee went for a family session re impending marriage adjustment on the fiancee's card, and the mother is not privy to therapeutic consultation notes, only that it occured, or the psychologist may have seen the child with verbal billing authority, some mental health coverage has no cards, bills are submitted directly from the provider.
A lot of assumptions have been made, please remember there are other rules that apply to mental health treatment and access to that information or records.