Why is my parent beginning to feel the past is as real to her as current time?

Get Netflix to watch Black Mirror San Junipero, s3e4.

From the mind of every protagonist, everything about San Junipero is not only real, but ideal. If you’re in your 50s, you too will think it’s real watching the character bang on her 1980s Mazda Miata.

The soundtrack is Heaven is a Place on Earth. It turns out San junipero is a ai simulation in which the consciousnesses of the dead (the town residents) and the dying (the so called tourists) are uploaded to around 2045.

Now and until then, some elders retreat into a San Junipero of their own making, which is absolutely real for them.

Because with dementia and Alzheimer's, the patient regresses back in time to childhood. It's the way the brain disease progresses. Your parent is now living IN that period of her life when you may not have even been alive, meaning she may not recognize you as her child. Go with it...enter her reality now and don't correct her.

The past has been there in the memory cells longer is how I think of it.

With Dementia you short-term memory is the first to go. All they have is their long-term and as the Dementia progresses even that lessons. I feel that they end up in their childhood. My Mom eventually did not talk about my Dad. A woman who knew our family was talking to her about Moms kids. Mom looked at her and said "I don't have any kids". Not sure who she thought I was.

Becasue with dementia there is no rhyme or reason as to what a person thinks or feels. They no longer process thoughts and actions the way they did.

Asking 'why' is as pointless as asking 'why me'. There is no real answer.