There could be. However, the quality can vary greatly. Some might be really well - written, with interesting crossovers between the magical world of Harry Potter and the Sailor Moon universe. For example, the author might give fem Harry some of the powers or characteristics similar to Sailor Moon characters. You might need to dig through a few stories to find the gems.
One common theme could be transformation. Just like Sailor Moon transforms, fem Harry might have a similar kind of power - up or transformation in the story. Another could be friendship. Combining characters from both universes means new friendships can be formed.
In fem Harry Potter and Sailor Moon fanfiction, a common trope is the friendship - building aspect. The characters from both series have to learn to trust and work together. This often involves some initial misunderstandings and then a deepening of their relationships. Also, the 'hidden identity' trope is quite popular. Maybe fem Harry has to keep her wizarding identity a secret in the Sailor Moon world or vice versa.
You can start by looking on fanfiction websites like Archive of Our Own (AO3). It has a large collection of fanfics, and you can simply search for 'fem Harry Potter and Sailor Moon' in the search bar. Another option is FanFiction.net, though the tagging system might require a bit more digging. Some Tumblr blogs also curate and recommend such fanfictions.
I'm not entirely sure if there is a large quantity of such fanfiction. However, considering the popularity of both Harry Potter and Sailor Moon, it's very possible that some fans have written stories in which they merge the two. It could involve Harry Potter characters showing an interest in Sailor Moon's magic system or vice versa.
One common theme is the combination of magic. Since both series have their own magic elements, fanfictions often explore how they can work together. For instance, spells from Harry Potter and the powers of the Sailor Scouts might be used in unison.
One could also write a fanfiction about a school exchange program. Hogwarts students could visit the Sailor Moon Cosmos schools and vice versa. The cultural shock would be huge. For example, the Hogwarts students would be used to using wands, while the Sailor Moon Cosmos students might use their transformation powers and magical items in different ways. There could be some friendly competitions between the students of both universes, like a magic - using race or a knowledge - based quiz about different magic systems.
Sure. There is a lot of fanfiction out there that combines these three universes. For example, a common theme is the characters from different series teaming up to fight a common enemy. In some fanfictions, Sailor Moon might use her powers to help Harry Potter in his battle against Voldemort, while Ranma could bring his martial arts skills into play. It's really fascinating to see how different authors play with these crossovers.
One possible plot could be that Voldemort teams up with a Sailor Moon villain. Harry and the Sailor Scouts then have to join forces to defeat them. They would bring together their different magical abilities, like Harry's spells and the Scouts' transformation powers.
It might have Harry Potter secretly collecting Sailor Moon merchandise in her dorm at Hogwarts. She could be seen comparing the magic in her world to that of Sailor Moon. For example, how the spells in Harry Potter are different from Sailor Moon's attacks.