The heroine does not travel through time. It was the child that Professor McGonagall and Dumbledore picked up from the ruins of the orphanage.
Voldemort destroyed the orphanage where he had stayed before killing the Potters.
A magical genius, she ended her Auror training at the age of eleven and became the youngest Auror in the history of magic.
And her first job is to protect the Boy Who Lived.
So she became a new student at Hogwarts, returned to the place where she grew up, and started her career as a bodyguard.
Piece: I'm really incompetent in naming it. I pulled out my hair when choosing the title of the novel. Then. Let's just settle it like this.