My wife works with people with dementia and tells me about it but I am no expert.
However it seems to me that if your mother BELIEVES that Carol Vorderman gave her breakfast it is best to along with it.
Otherwise you are constantly going to be contradicting your mother, which will not be nice.
Sadly some of the symptoms of dementia can cause people to "see" things that are not there (one of the people my wife worked with kept seeing his brother sitting in a car outside, when they went outside to see the car it was empty but he still insisted the brother was in the car).
Other problems can be the person with dementia forgets who you are so might believe you are a burglar or have come to attack them.
One dementia patient my wife worked with tried to strangle his wife with a seat belt (he was in the back) as he though she was kidnapping him.
So it is best not to argue with dementia patients.
A book called My Bonnie by John Suchet is well worth reading, one of the most amazing books I have ever read. His wife got dementia at a young age. It is a love story, a funny story, and a moving story.
Amazon.co.uk User Recommendation