Hi Channy,
I have had a pretty stressful day in Dementia Land myself, so my reply may be off the mark.
If my husband had read your post (which he hasn't), he would tell me NOT to correct my mother, that there is no point, and setting her straight is one way to create upset, further obsessing and an argument.
I pass this golden advice on to you. If you point something out to the person and they won't accept what you say..... even if you are in the right...... just drop it. A case of least said, soonest forgotten.
What stage? I don't really hold much truck with this stage business. I think professionals use this as it helps them to look knowledgeable. As if they know where we are in this disease. Mum is just entering 'severe' stage, stage 6 they call it, I think, though not stage 6 in France (see what I mean, even specialists can't agree on this), and she is no longer able to work things like this out. At least your Mum is thinking, attempting to plan, even if she gets locations, times and place wrong.
I can imagine how upset you feel. It always bowls us over when they start displaying behavior that is clearly wrong. I was tugged right out of my comfort zone and had to look dementia in the face. Obviously I had hoped to see Mum, but dementia had momentarily taken her place.
Today was an off day for me because Dementia was centre stage today, flaunting antics at every turn, and each behaviour a new one. Not a great day for me. The blessing is Mum remains largely unaware of this - she deems all normal, and still says she is in perfect health with no memory problems.
Hope your Mum has forgotten her appointment abroad tomorrow. Easier that way for both of you. Take care, BE