How do you stop your mother who continues to repeat stories and history from the past?

Strange how that works but it's VERY common and nothing to be overly concerned about.
The record gets stuck. They can't remember yesterday but 70 yrs. ago is fresh in their mind.
Could be they choose to remember the good / fun times and not the hard / responsible times.
Just pray she doesn't tell you all about her sinful stuff. That can be painful & I excuse myself from those stories.

My mother does, she is 86 and goes on about clothes she had when she was 14 and the dances she went to. She takes out a photo and it sets her off. My grandmother was the same she used to talk about when she was a child but could not remember how old she was. My mother is going the same way - days of the week escape her and her age is getting fluffy memory wise but she can remember all her childhood. She talks about her 8 brothers and sister and my dad and brother (all gone now) and it does her good - memories should be shared - it keeps people alive in your heart. It cheers her up too so that is not a bad thing!

She might have early dementia.Dementia doesn't always mean someone has obvious memory loss. There are other signs, such as repetition. According to info I learned from the Alzheimers Association not all older people show the symptoms we commonly consider" just getting old." This organization has lots of helpful(free) info, classes.

My other comment/question is, does this storytelling bother you ? If so, try helping her get new experiences to enjoy and remember.
Good luck!

Yes my Aunt does and she is 93. We love to listen to the stories and we now encourage my Mother who is 95 and her sister and cousin (91). It is great to hear the stories and we are sharing with all in the familu