First off the bat in the post I replied to you actually said
"When we talk about our work day, we share relevant details we wouldn't disclose to anybody else, so the answer is yes. If it's been interesting, important, or otherwise been a key moment or part of our day, we would chat about it and know it's completely between us."
Nothing there - or in any of your previous posts where you're arguing that divulging a friend's personal confidence to your husband is not only reasonable, but an important facet of a loving relationship - that would've lead me to believe you were carefully filtering out any identifying details.
Secondly (and as you rightly point out in your post) when clinicians talk about patients - even when anonymised - it's invariably to other clinicians that share the burden of confidentiality, and not at random social gatherings or coffee mornings with miscellaneous friends. The same can be said for most occupations, when teachers need to burn off steam about challenging behaviour from students, they talk to fellow teachers etc.
And to answer your question specifically if it's acceptable for, as per the example you gave;
"In fact, we have a friend who is a teacher who often talks about challenging pupils, some that make her life really, really hard. It affects her and while confidential details about their diagnoses or home lives can be relevant, they're anonymised."
In my opinion that is absolutely not acceptable. It sounds as though she works with some pretty vulnerable children to have details about medical diagnoses and home lives. If she is struggling to cope with her job concerning specific students she should seek support from her colleagues or her direct manager, in extreme circumstances she should confide in her partner/closest friend under the strictest confidence or seek a therapist. She should definitely not be gabbing about it with a group of pals.
As your posts exemplify, people talk (gossip). The people she discusses these things with pass it on to others and who knows what can be identifying to others.
Honestly, I find it quite appalling that she would do this. If I were her manager I would hit the roof and bounce back a couple of times.