Can I tell you how it was for us? Following all the tests at Mum's first Memory Clinic appointment, the Consultant told us first of her findings (probable AD, early stage) and we were asked how we thought Mum would take the news if they also told her. I had no idea how she would react, but felt that she should also be told. I think they did tell her because we then all met together to discuss the next steps (Aricept etc), and on the way home, I remember talking to her openly about the diagnosis. She just seemed to 'accept' it all, said yes and no in all the right places, as though it were all happening to someone else, and I was never sure if it had really 'sunk in'.
Since then, there hasn't seemed to be much point in talking of the diagnosis, and I very much doubt she remembers. We just say 'memory problems' if the subject comes up. I think I could tell her anything and she would just accept it because she doesn't seem to understand anything in too much depth -though to talk to her you wouldn't know it since she has all the right answers/replies in all the right places. Sometimes, we will see something on TV about an Alzheimer's sufferer, and Mum feels so sorry for them ..'poor soul', she'll say.
So I believe I could go over and over the diagnosis, each and every day, reminding her, but she wouldn't understand, even if she said she understood. Does that make sense?