Is it beneficial to suggest my Mom keep a diary?

She kept one until 10 years ago. Her dementia started about 8 years ago. My Mom still recognizes family & close/old friends, but her short term memory is totally gone. Most anything that occurred in the past 10-15 years is gone. She is generally in a good mood, although she sleeps ~15hrs each day and has no energy. She has suffered a number of mini strokes, but she shows no signs of them (the doctor says she is compensating very well and is equally strong and coordinated on both sides). She kept a diary from '94 until 2005. During this time she went through 2 rounds of cancer and chemo. She doesn't really remember having cancer. So my question is 2 fold; should I show her the old diary (I found it in a box of old photos that was in storage)? Should I suggest she start a new diary? Thank you for any insight and suggestions.