Yang, please share with your T about your difficulties with the receptionists. You are doing your T a favor by letting her know about her staff because they could be driving her clients away and degrading the success of her practice. Also, it is not "bad-mouthing" the receptionists if what you say about them is true. Bad-mouthing is when you say something bad about a person that is not true.

Side story: I had a dentist once who was a nice guy but his receptionists were rude and awful. I got stressed out every time I had to deal with them. Finally, I changed dentists to avoid the situation (he was an OK dentist but not great so it was worth the switch). One of the receptionists called me up to bawl me out for changing dentists! (She had got the request from the new dentist for my records.) She said it was unethical for the new dentist to "steal" me away, and she was going to "report" him to her employer. I said go right ahead but also please add that the reason I am leaving your employer's practice is because of all the problems I have had with you and other staff and I would be happy to return as his patient when he fixed that. She hung up on me. Anyway, just wanted to share that as an example of how staff can drive customers/clients away. You are really doing your T a big favor by telling her the facts.

Ummm, why on earth would you apologize for missing the session or offer to pay for it? You didn't miss it--you were there on time. If anyone should offer to pay, it is T who should offer to pay you for the time you wasted... I hope that your sharing this experience with your T resulted in her reprimanding staff.