Hi Johnprem, welcome to TP. I think Stanleypj is right receiving a diagnosis is devastating even though you may have been living with the disease and its symptoms for some time.
I have had symptoms for 6 years now and have also cared and still do for people with dementia. Until I had my own symptoms, I can only say I had no idea of what sufferers go through - as an 'onlooker' it seems they go out of their way to upset you, become lazy and want you to do things for them, forget when you ask them things etc. etc. I now know the reality: all energy and mental effort goes in to trying to cope with day to day living whilst struggling with a brain that is constantly misfiring at will is as it seems. Lots of help and support is needed, but not really wanted, thank you, as one struggles to do what the mind has always wanted to do.
If your Mum was never one to 'play on' things before I'm sure you can safely say she is not doing so now but that the illness is affecting her functioning so much. Some people don't want to talk about their diagnosis but as with any other illness not sharing about such a devastating diagnosis can cause severe depression. Keep posting it will help your understanding.
Best wishes
Sue