I'm sorry I didn't post earlier, I saw this a few days ago, but didnt have a good answer, although the story was disturbing.. I so sorry you and your ds had to go through this, and for the teacher
I'll post my first thought, I've been thinking about it for a while, and I still come back to it
I would COMPLETELY remove everyone connected to the situation, mutual friends of the teacher etc.. from my life. That's just me, but she sounds shady. I dont' like it one bit. I would keep your ds away from this woman. I think she's toxic so to speak. Just the fact that you were so nervous and shakey when you saw her was a red flag. I'm glad your ds is out of the environment, but I'd made every attempt to get her completely out of your life 100 percent.
I do believe she indeed traumatized you. I have PTSD, and I have "triggers" pretty much anyone related to the incident, triggers very scary emotions. I would seek treatment from a counselor who is TRAINED AND FAMILIAR WITH PTSD!!! not all of them are. Ptsd is pretty complex, so I would not do this alone, no way, but that is just me. Hugs!