Just because it did not happen to you this time does not mean she has not made it a hostile work environment for all of you. Discuss your concerns with your pharmacy supervisor. Let him know that you're very uncomfortable (and it's probably helpful to get other employees who are uncomfortable in on this conversation with him) and that it needs to be addressed in some form. She is harassing you as well, trying to get you to apologize to her for something that is ridiculous, etc. She has a history of abuse of all your employees.

"Pharmacy supervisor, I was hoping we could talk this afternoon when you get a minute."
"I have some real concerns about customer XYZ. After what happened the other day to Jane, I think many of us are feeling uncomfortable about the situation. Can we please escalate her behavior to the district manager and HR? I know I'm not the only one that feels that she is abusive of our staff and is making this a toxic work environment when she is around."

How your boss responds depends on your course of action from there. If your boss agrees to contact the DM and corporate, give them some time to address it and ask them to keep all of you techs apprised of the situation because you're all concerned and want her behavior addressed. In the meantime, document everything when she comes in. Do not take it home, as her name and information is still protected under HIPAA. Just a short basic time and actions "11/13/16 11:06AM - stated she was dissatisfied with service and we all better give her an apology for what we've done." Put it in the drawer at work, or give it to your pharmacist to keep track of so they can eventually reference if needed.

Don't worry about your pharmacist being stressed - this is a learning experience for him too. He needs to be able to help you guys, he's your boss and he is an important part of making a safe work environment for his employees. Just because you like your boss does not mean you have to put up with harassment. I don't think you're being nosy or looking for an excuse to leave (though if you want to leave, you don't really need a reason to), I would be uncomfortable in this situation as well.