The biggest challenge might be changing Tom Riddle's fate. Since he was destined to become Voldemort, Fem Harry has to constantly be on guard against the dark forces that might still be attracted to him. She has to find a way to replace his thirst for power and immortality with more positive desires. This means she has to not only be a caregiver but also a mentor and a protector, all while trying to fit into a time period that is very different from her own.
One challenge could be dealing with Tom Riddle's existing personality traits. Even as a child, he had a certain cunning and pride. Fem Harry would have to find a way to work with these traits and not trigger his darker side. For example, if she's too strict, he might rebel in a more negative way.
She would face the challenge of dealing with Tom's own nature. Even as a baby, he might have some of the traits that later led to his dark side. Hermione would have to find ways to nurture his good side and suppress the bad. Also, she has her own life and studies. Balancing taking care of a baby and her own development would be difficult.
One challenge would be dealing with his natural inclination towards power. Tom Riddle has always been power - hungry, and Fem Harry Potter would have to constantly find ways to redirect this drive in a positive way. For instance, she might encourage him to use his power for the good of the wizarding community.
One common theme is redemption. Since Tom Riddle later becomes Voldemort, the idea of fem Harry being able to change his path and redeem him is often explored. It gives a sense of hope that even the darkest of characters can be saved.
One popular 'fem Harry adopts Tom Riddle fanfiction' is 'A Different Kind of Family'. In this story, the female Harry takes Tom under her wing in a really interesting way. It explores how their relationship develops over time, with some unique twists on the magic world we know from the original series.
Perhaps in the fanfiction, Harry adopts Tom Riddle when he's still a young boy at the orphanage. Harry then uses his own experiences of growing up without parents to bond with Tom. He teaches Tom about magic in a different way than Dumbledore did, focusing on the positive aspects of magic for good. This could lead to Tom not becoming the evil Voldemort we know.
Some Harry Potter - themed forums also might be a good place to search for such fanfiction. There are often threads where fans share their favorite stories or even post their own works. But be aware that the content on forums might not be as well - organized as on dedicated fanfiction platforms.
The allure often lies in the novelty. It's exciting to see how the story changes when Harry is female. For instance, the way she interacts with Tom Riddle can be completely different. She might be more empathetic towards him in some fictions, which could potentially change the course of his dark journey.
The story could take many directions. Fem Harry might try to find out what went wrong in Tom's early life that led him to become Voldemort. Maybe she discovers some family secrets or hidden traumas. And as Tom grows up under her care, he could start to develop a different personality. He might become more empathetic and less power - hungry because of the loving environment Fem Harry creates for him.
She might have trouble adapting to the past's way of life. The technology and social norms could be very different, making it hard for her to fit in.
One great fem Harry and Tom Riddle time travel fanfiction is 'Time's Twist'. In it, fem Harry travels back in time and has to navigate the Hogwarts of Tom Riddle's era. It has a really interesting dynamic between the two characters as they try to understand each other.