I'm sorry, I guess I still just don't get it. Maybe because I wasn't there. You went to the initial visit. You found out that you had to pay cash and that had to file your own paperwork. Now you're upset because you had to pay cash and file your own paperwork. It seems like she did what she said she would do, which is to provide massage for cash.
I was in a bad auto accident. Part of my treatment was massage prescribed by the treating physician and paid for by the driver's insurance who caused the accident. I was very careful to call around all the massage therapists and ask if they took insurance cases. Most said no. I found one who did and spent some time on the phone to be absolutely sure she understood and agreed to be paid by the insurance company and to do all the paperwork herself and wait to be paid. I knew I couldn't pay and could not take the stress of dealing with the paperwork. Only then did I make an appointment. It took her six months but she got paid and did all the paperwork.
I just don't know why, if you were seeing someone on a cash basis and had to file the receipts yourself, and if the money was such an issue, why you didn't work out with the insurance company exactly what you needed to get reimbursed without rejection and then make sure you left each visit with that paperwork or stopped seeing her if you didn't get the paperwork. And why you went on to keep making appointments after not getting that paperwork on the second visit. I don't understand why you let things go so far, as the amount of money you're talking must be, what, 20 or 40 visits? This doesn't make sense. I don't get it why using the filing against the therapist is the answer because you didn't take responsibility for the paperwork when you knew from the first visit that it was your responsibility. I just think it's an abuse of the process to file against someone because of your feelings and that you're stressed.