Another theme is often the character's journey in a different light. A female Frodo might face different challenges or be perceived in different ways during the quest to destroy the ring. This can add new layers of depth to the story and her relationships with the Fellowship members.
One interesting crossover could be a magical item from the Harry Potter world ending up in Middle - earth. For example, the Marauder's Map might find its way into Frodo's hands. It could help him detect orcs and other enemies in a different way than the normal methods in Middle - earth. Another idea could be a wizard from Hogwarts traveling to Middle - earth and using their magic to assist Frodo on his journey. They could use spells like the Patronus to fend off the Nazgûl.
Definitely Harry and Frodo. People love to see how these two heroes from different universes interact. Harry, with his Gryffindor courage, and Frodo, with his hobbit determination, make for an interesting duo. They both have the weight of the world on their shoulders in their respective stories.
You can try fanfiction websites like Archive of Our Own (AO3). There's a large collection of fanfics there. Just search for 'female Frodo Baggins' and you'll get a bunch of different stories to choose from.
Here is a simple fanfiction: Harry and Frodo met in a strange magical forest. Harry was on a quest to find a new magical artifact, and Frodo was still carrying the One Ring. They decided to travel together for safety. Along the way, they shared stories of their different worlds. Harry told Frodo about Hogwarts and magic spells, while Frodo told Harry about Middle - earth and the great battles against Sauron. Their journey was filled with challenges and new discoveries.
In bella baggins fanfiction, the character of Bella is usually made to be very brave and resourceful. She may have to face challenges like orc attacks or difficult terrains. Also, these fanfictions often explore relationships, whether it's between Bella and other hobbits or with characters from other races in Middle - earth. For instance, her friendship with an elf or a dwarf could be a central part of the story.
Frodo's life was a sad story because he was a simple hobbit from the Shire at first. He was happy there, but then he was thrust into this epic adventure. He had to endure long and arduous travels, face terrifying creatures, and deal with the psychological toll of the Ring. In the end, even after achieving his goal, he couldn't fully recover and had to leave Middle - earth. His life was forever changed and scarred by the events he went through.
Friendship is a very common theme. Sam and Frodo's relationship is iconic, and fanfiction often explores the depths of their loyalty and care for each other.
I haven't read this novel specifically. But generally, in Tolkien - related works, Frodo's encounter with the Black Riders is full of suspense and danger. The Black Riders are terrifying foes, representing the power of Sauron. Frodo's journey in such a context often involves a test of his courage and the will to resist the dark forces.