Do you tell mum?
My mum was diagnosed 5 years ago. My dad cares for her. She has always been aware that her memory is very bad. Even now, she will say "what's up with me, why can't I remember?", but within a few minutes, she has forgotten she has said that. Thus, I can't see any reason to tell her as she would only forget anyway! There would be brief momentary shock and then she wouldn't remember. She had breast cancer around the same time as the diagnosis and had to have a lump removed. She doesn't remember that either. Thankfully despite alot of problems, she still has a sense of humour, she will say "I'm going bloody ga ga aren't I! I could never see the point in telling her. She is happy in her own way and is also always saying "thankfully I keep pretty well, you have to count your blessings". She goes to the local Alzheimers day centre, but never questions why she does there, because by the time she comes home, she has forgotten. She suffers from incontinence and when we went to see a specialist, she was utterly disgusted when he asked her if she realised she had a problem, as again, she doesn't remember. So I can see little point in telling her. I hope that is of help to you.