To have told my sister she was unprofessional and inappropriate? * [Content warning: concerns baby loss]

It actually doesn't matter what the photo was of. Its a breach of confidentiality and she should be dumped in the shit for doing it. I am not sure about the next bit but its possible that the people in your chat could get into trouble for receiving and presumably retaining the image. Do be careful OP.
Additionally, it doesn't matter about who took the image and it doesn't matter about "nurse dark humour" a breach is a breach.

Autism is no excuse if that's the case. Stop using it as an excuse!

No, she's just disgusting. Can you report her?

A PP guessed rightly that she was an estate agent. There must be other estate agents on here, if so have you ever known colleagues to do this kind of thing?

She is completely unsuited to her job. No doubt she will have been instructed as to how to behave in such cases. Her employer should be informed and she should be sacked. She is also a v. nasty person. She may also be breaking the law re. posting pictures of child.

In that case do the one thing she’d hate: give her less attention. Grey rock her when you see her. Don’t go out of your way to message her. Don’t arrange to see her for a while. Be less interested in what she has to say or what she’s up to.

TBH I’d have to do that because I’d struggle to look her in the eye ATM.

This is just arguing for the sake of it.

Why can’t people put the wronged side first for once.

I would report this and send the evidence to her employers. She could lose her job, family might blow, up so what ?
She's a disgusting piece of shit.

She has no children. Yes, I think we could have guessed this.

This is classic DARVO OP if you haven’t heard of it (Deny, Attack, Reverse Victim and Offender). So when she’s criticised she turns it back on the other person. It is consistent with people with narcissistic traits. It’s done partly so they don’t feel the shame of having done the bad thing and pass it onto the other person and partly to train them not to criticise them again.

Your sister is a vile excuse for a human. I wouldn't be "gently" telling her anything. I would be telling her how utterly disgusting and callous a person she is to refer to a deceased child in that manner. I would find it hard not to feel anything but contempt for her going forward.

Your sister is the lowest of the low. Mocking a deceased baby. You probably won’t, but should show her this thread. Though by the sounds of her she will still think she has done nothing wrong.

Nasty, intrusive and totally unacceptable. She's a guest in their home, she's crossed a line and in such bad taste. It's also illegal to photograph things in a private place and stick online. Am pretty sure home owners would not have consented. She had better be careful she doesn't put it anywhere else.
She doesn't like being pulled up on bad behaviour eh? That's her issue.

That's horrible OP. She shouldn't be taking or sending any photos. No decency and I'd feel the urge to distance myself from her.

Edit after your update - the permissions given for photos to be taken is for the purposes of selling the house, and to be stored and shared for only related things. She doesn't have consent to share and use as she has and it's a huge breach of trust.

Don't know why you felt the need to ‘gently’ tell her…. What she did was appalling.

Omg 😦 she’s a vile person isn’t she. Who made her the Judge?

Maybe go to her house and when she isn’t watching film around the worse bits of her house and put them on the chat! I’m sure you will be outraged!

Your sister's complete lack of boundaries or basic empathy will catch up with her at some point.

To mock them.

What with the caption “it’s dead”?

This and I would screenshot and pass it direct to the employer. I would stake our relationship on it - that a total invasion of privacy the fact she didn’t immediately delete it when challenged speaks volumes

It's obviously highly unprofessional and unethical as well (as is sending pics of people's dirty homes) but is it possible that she was heart broken and upset for her client and wanted to share that with her family? She still shouldn't have done that or course but I just can't think of any other reason why someone would do that?

I mean sending videos of dirty houses etc is already bad enough but to send a picture/video of someone's dead baby is jaw dropping and utterly appalling.

Send your sister a link to this thread so she knows just how wrong she's been.

I agree with this. It needs to stop and you are the only one who can stop this. You either have a real face to face with both her and the family or you report her. Or both!

I have worked in the NHS and confidentiality and dignity are fundamental to the service. I don’t know about others but there are things I saw and experienced that I have never and will never speak about to anyone.

A deceased baby and the families grief have been exploited here. How dare she!