At the beginning what did you do about telling people about your loved one's diagnosis? Mum visited her niece yesterday (we don't have a lot of family left now as many of them have died or don't keep in touch). She mentioned to me on Facebook that mum had repeated the same thing a few times. Also she talks to her neighbours who have mentioned to me they have noticed some confusion. I feel disrespectful to mum telling people so I just brush over it a bit upto now. I know mum would be mortified if I tell people (I know she won't tell people because she doesn't really understand it). Did you tell people or just let them figure it out for themselves?
In my mother's case told everyone who might need to know (neighbours etc.) but asked them not in any circs. to mention it to her, since as far as she was concerned there was nothing wrong with her and it would just make her angry.
I too felt disloyal but when someone might be behaving oddly then I do feel anyone close needs to know so that they can make allowances.