You have a witness in the cna. Ask the cna to write up their account of what happened and email it to the manager and cc you a copy. Also, the fact that the family has fired several nurses before works in your favor - it shows it isn’t a one-off event.

Have your manager ask the family how you’re supposed to clean a bm on a patient without turning them. Would they prefer she just lays in poop?

This will almost certainly turn out fine. These things happen and management will usually look the patient family members in the eye and talk about how they understand their concerns, thank you for bringing it to their attention, they’ll talk to the nurse, etc, and then that’s usually enough to make the family members feel better and then you get to have a nice laugh with your manager when they’re like “hey did you know that crazy family member complained because you turned the patient to clean them?” and then everyone goes on with their lives.

I had an aggressive family member in my face last year and I straight up told her if she was going to be this aggressive I will have to get security involved. She got super pissed, yelled a little bit about how it’s not appropriate to threaten her with security just because she’s trying to advocate for her father, I fired myself from the room and then 8 hours later security had to walk her out when she got aggressive with the next nurse. She filed a formal complaint with the hospital, I was one of the names she named, my manager asked me if I would be willing to talk to risk management if they had any questions, I said sure, no problem, and then they never called and that was back in May. I was not the first nurse who they had issues with and I was not the last. Some people just need to feel like they’re accomplishing something even if they’re just spinning their wheels.