I got a call back from the practise manager and, after much debate, a few heartfelt words and some clarification, she offered to wipe the slate.
I accepted that they were acting in my daughter's best interests [apparently she needs a root canal on that tooth or a removal] and they accepted fault for not contacting me for permission to go ahead with any further treatment.
It was all worked out and now we have a new appt. for this Friday with my regular dentist to discuss options for treatment.
Thanks to all those who commented for the support. You enriched my... backbone. :)