This is not a Voldemort transformation/redemption story. The heroine is just a bystander and does not change the plot. The following is a synopsis:
1937, orphanage
"So you're from the future?" Tom Riddle asked.
"A very, very far future. But don't worry, I'm just an avid history buff. I will not and have no ability to interfere with the process of history." Bertha answered while recording it in her notebook.
*
October 31, 1981, late
Bertha still held the notebook: "How are you feeling now? I must say that this is an extremely important time point."
Voldemort stood in the Potter family's hiding place and gave Bertha a false smile.
*
1992, June
Voldemort grabbed Bertha's neck: "You already knew it."
Bertha was not affected in any way: "I have known it for a long time, and you know that I have known it for a long time. So how do you feel now, being defeated by an eleven-year-old child?"
*
1998, May
Bertha stood in front of Voldemort's tomb, closing her notebook with complicated emotions.
(Stayed on August 21, 2022, probably the third HP, I don't know when it will be released)
Purpose: Love life