OP, I’ve read your update.
Please, please do take this further. I understand how difficult it feels when one is not the type to make a fuss; and then your family dynamic compound this. Nonetheless, there is only one right choice to make here, which is to take it further. If you wish, add that you personally wouldn’t want the nurse to lose her job and just want processes to be reviewed and training to be given so this never happens again (the actual outcome is out of your hands but things would be thoroughly reviewed and you could be confident that the nurse would only lose their job if it was unsafe for patients for them to continue working).
You can also explain you wouldn’t want your name to come in (the hospital will have their own internal patient safety concern process and the fact this relative was calling and turned up when no family had told her your child was in is more than enough for that to be instigated from the internal framework).
The theatre nurse has shown a truly dangerous lack of judgement here and it is not safe for this incident to be swept under the carpet. You, as your child’s advocate, owe it to them to do this. Future (and potentially past, as this is often a pattern) patients would also thank you.
After this horrible experience, imagine how much the validation of receiving an acknowledgement and apology from the hospital could help your child. How it could help your child to know steps were being taken to stop this happening again – to them (heaven forbid) or anyone else.
If you don’t, you are communicating to your child that you would rather kowtow to your husband’s unreasonable wishes and a stranger’s welfare than stand up for them when something very wrong was done to them. Their privacy and safety were violated when they were at their most vulnerable. If this was you, would you then want to go back for another treatment at the same place if you ever needed or would you be terrified? Would you confide in your mother again? Perhaps worse, would you internalise that behaviour and go into adulthood having learnt a message never to rock the boat, even if this is at the expense of your own wellbeing and that of any future dependents?
I apologise that this may come across as harsh. I feel for you and you must be in turmoil. It can be hard to see things when you’re in the middle of things, not least after the horrible stress of the operation itself. But from the outside, trust me when I say it is abundantly clear there is only one good choice to make here. I wish you all the best.