It must be interesting (although sad) to re-read old diaries and journals to see when subtle signs of dementia began to appear in your wife. When I think back there were some oddities and lapses in my mother which I'm pretty sure were early signs of her AD. For example:
-misinterpreting hearty stamping and applause by other pupils for a soloist entering the hall to play in a school concert as hostile rather than supportive (this was very early on)
- apathy on a garden tour when my mother had always been very interested in, and knowledgeable about, plants and gardens
- not remembering to meet me back at a particular place in the Royal Albert Hall after going to the lavatory (I had to search for her in that huge place)
- saying that she did not know how to turn the central heating on after complaining that she was cold
- not remembering to pick my daughter up from somewhere
- not being able to find her way to my daughter's drama class even though I had shown her the route
- not understanding that her passport had not expired (could not understand that because the expiry year was 2012 it was still in date although it was April which was after January)
- getting so agitated at the airport about a journey to Belfast that she had done multiple times that she had to be put in a wheelchair (when she was perfectly fit) and accompanied to the plane
I explained these things away or got annoyed with my mother. It did not occur to me that these might be early signs of dementia. I was slow to face up to the situation until things had become quite unsatisfactory. If my brother and sister had not been living abroad at the time perhaps we would have got together and recognised that my mother had a problem earlier.
Another way of tracking my mother's decline is to remember how her journey to and from our home required more and more involvement by us (eg walking her to the station at our end, dropping her off at Kings Cross station for her journey to her home town) until, eventually, she could not make the journey at all.
It is the inability to problem solve at even a basic level which is a red flag for me.
Peter, I can't see that anything that you did or said accelerated your wife's decline. She has an illness which has its own trajectory in terms of progression. Try not to torture yourself. The changes in the very early stages are often subtle and not recognisable to anyone who does not already have an intimate knowledge of dementia and, therefore, the person can seem moody, anxious, self-absorbed, 'selfish' 'lazy', neglectful of his or her personal appearance and hygiene or unaccountably 'stupid'; clear evidence of actual memory problems may not be apparent. If the person lives with a partner the partner may, without realising it, do more / take over / prompt or remind and the problems are masked to some or a large extent until the changes in behaviour become too great to ignore or explain away. People who live alone can't really cope with the demands of day-to-day life and can become extremely anxious even when the dementia is at an early stage.