What are signs of early confusion in mid-60s?

Something really strange happened last night. My wife in her mid-60s no longer remembered that she liked Pepperoni Pizza. Before you dismiss this as nothing, she really liked pepperoni pizza for many, many years, and we ordered half that way for her. I always ordered mine plain. For many years, she even went out to buy pepperoni extra for herself to eat at home, which i never touched. But last night, I did the same, we had a lot to do, and I was caregiver my 80s my mother with Alzheimers, and my wife suddenly thought I ordered the pepperoni for me. She thought I liked pepperoni and she didn't. I have seen other signs of confusion lately, which I thought were mostly her ADD. She seems to forget we have watched TV shows or movies if it was not recently. Should I be concerned? I was taken aback how determined she was that I ordered pepperoni pizza. I am really sorry if those of you, like me who are serious caregivers of major dementia, think this is trivial. But it was sort of stunning. What do you think? Is this the type of thing I should be concerned about? My mother's Alzheimer's Disease was so obvious and graphic, there was never any question about her level of dementia, just how to cope with it.