Perhaps she wants to understand Voldemort better. In Britain, she's only heard one - sided stories. By going to him, she hopes to find his weaknesses and also learn more about his rise to power, which could help her defeat him in the long run. It's a risky but potentially effective strategy.
It could be that she feels alone in Britain. All her friends and allies seem to have their own ideas about how to deal with Voldemort, and none of them match hers. So, she leaves Britain to face Voldemort, believing that she can make a difference on her own, away from the constraints of the British wizarding community.
She could be frustrated with the Ministry of Magic in Britain. Maybe they're not taking Voldemort seriously enough or are even hindering her attempts to fight him. So, she decides to go directly to Voldemort to end it all on her own terms.
There's 'The Journey of Fem Harry Away from Britain'. In it, Fem Harry decides to leave Britain as she believes she can't grow and fight Voldemort effectively in the environment she's in. She may encounter new allies and enemies on her journey away from Britain. Maybe she meets some foreign wizards who have different ways of magic that could help her in her fight against Voldemort. And then there's 'Fem Harry's Departure'. This fanfic could explore how her leaving Britain is a strategic move to draw Voldemort out of his comfort zone and into a new battlefield.
One reason could be the media attention. After all they've been through, they might be tired of constantly being in the spotlight. The British wizarding press could be hounding them, so they leave to get some privacy.
One reason could be to escape the constant reminders of his past traumas in Britain. The place is filled with memories of Voldemort and the battles he fought. Maybe in the fanfiction, he just wants a fresh start away from all that chaos and danger.
One reason could be to escape the lingering dark magic and the constant reminders of their past battles. Britain, especially Hogwarts, has seen so much turmoil that they might feel the need for a fresh start. Another reason could be to explore the wider wizarding world. They've been mostly centered around Britain in the original stories, and in fanfiction, they could leave to discover new magical cultures and spells in other parts of the world.
In some fanfiction, Harry leaves to seek more powerful magic. He realizes that the magic in Britain is somewhat limited in the fight against Voldemort. So he travels to other places, like ancient magic - rich regions in Asia or Africa, to find a way to defeat Voldemort. He hopes that by leaving, he can gain the upper hand in the battle.
One common theme is self - discovery. When fem Harry leaves Britain, she often has to figure out who she is outside of the expectations and restrictions of the British wizarding world. For example, in many stories, she realizes she has different magical abilities or interests that were suppressed in Britain.
There's a fanfic called 'Farewell, Britain'. Here, fem Harry leaves Britain because she feels that she can no longer tolerate the false accusations and the dangerous situations she's constantly in. She heads to America where she discovers a whole new world of magic. It's full of adventure as she meets new friends and foes alike. It also explores her growth as a person outside the familiar British magical world.
The relationship may develop through a series of challenges. For example, they might face opposition from both the Death Eaters and the Order of the Phoenix. This external pressure forces them to rely on each other more. Fem Harry uses her intelligence and courage to help Voldemort face his inner demons, and Voldemort uses his power to protect Fem Harry from those who want to harm her. Through these shared experiences, their relationship deepens and evolves into a loving marriage.
The theme of forbidden love also often appears. Given their status as enemies in the original story, the idea of them having some sort of romantic or deep emotional connection in fanfiction is a popular one. It adds an element of drama and tension to the story.
The theme of trust is often present. Given that Harry and Voldemort are usually enemies, when it's a female Voldemort, the story might focus on how they learn to trust each other or not. And the theme of changing fate. They might try to change the fate that would usually lead to their enmity, for example by working together to prevent a greater evil.