The post-Soviet situation wasn't a paradise to be sure, but I doubt it had THAT kind of effect. I only mentioned it to say that the medical care she received back then was likely far from the quality people expect in the western countries. In the internet, the default assumption usually is that everyone is from the USA unless stated otherwise.

As for her precise diagnosis - that's not even what I'm seeking so much at the moment. From what I've heard, back then one label that was put on it was "paranoid schizophrenia", but I have no idea of how accurate that was, and our understanding of mental illnesses has also greatly expanded since then. It's quite likely that today she might get a different diagnosis.

What I would like to find out is... I don't know... some sort of direction to move in. Some ideas on what might be tried and what should be avoided.

What is the currently generally accepted best practice when someone has an obvious mental illness, but denies it and refuses to see a professional? AFAIK you can only force a treatment on someone if they become dangerous - but this is (thankfully) not the case.

About the space they share - It's a 3-room apartment. Not a very big one, but quite sufficient for two people. Can't avoid running into each other though. They've also lived there for the most part of their life. Moving to a bigger space... well it's an option, sure, but I think it would be pretty stressful for granny. I can't imagine at that age moving to a new place and making it feel like "home".