Perhaps a group of trainers who believe in a very strict and old - fashioned way of Pokémon training see the fem Ash as a threat to their ideals. They become her rivals not just in battles but also in trying to stop her from spreading her new and different ideas about Pokémon training throughout the region.
One potential rival could be a male trainer who has a more traditional view of Pokémon training and looks down on the fem Ash's different approach. He might constantly try to one - up her in battles.
Gary could be one of his rivals. Gary has always been competitive with Ash. Another potential rival could be a new character introduced in the fanfiction, someone who is really good at Pokemon battles and wants to prove himself better than Ash.
Some potential rivals could be the local Unova trainers who are known for their unique battling styles. For example, a trainer who specializes in using Bug - type Pokemon could be a tough rival for them.
One interesting plot point could be how the female Ash navigates the Pokémon world with a different perspective than the male Ash. Maybe she forms unique bonds with certain Pokémon that the original Ash didn't. For example, she might have a special connection with a more feminine - typed Pokémon like Gardevoir.
There are quite a few potential rivals. For example, Paul could be one. He has his own unique battling style and might be intrigued by Ash's Alola - champion ways. Then there's Trip. He could see Ash as a target to boost his own reputation. And in Alola itself, some of the more ambitious students from the Pokémon school who are aiming to be the best might also become rivals, constantly challenging Ash to prove they are worthy.
There could also be a mysterious trainer who appears from time to time. This trainer has a very powerful and rare Pokemon that Troy is intrigued by. Their battles would be intense as Troy tries to figure out the mystery trainer's strategies.
Another potential rival could be a young prodigy named Lily. She has a diverse team of Pokemon that she has trained from a very young age. Lily is very confident in her abilities and constantly tries to outdo Phoebe in battles. She might also have some unique training methods that Phoebe has to figure out in order to defeat her.
A rich and spoiled trainer who has access to all the latest Pokemon gear and rare Pokemon could be a rival. This person might look down on Cameron at first but later realizes Cameron's true strength. There could be a lot of tension and competition between them.
In Kalos, one potential rival for Ash could be a local trainer who specializes in Fairy - type Pokémon. Fairy - type Pokémon can be quite tricky in battles, and this trainer has mastered the use of their unique abilities. For Misty, a rival could be a girl who is an expert in water - type Pokémon battles, just like Misty herself. This girl might have some rare water - type Pokémon from Kalos that Misty has never seen before.
There could be a new, unknown group of villains in the fanfiction. They might be after a special type of Pokemon that is native to Unova. These villains could be using underhanded tactics to catch these Pokemon, and Ash and May would have to uncover their motives and stop them. For instance, they could be trying to use the power of these Pokemon for their own selfish gains, like taking over Unova's Pokemon centers or disrupting the Pokemon league.
Another possibility is a Torchic. Torchic is a fire - type, and it's small and cute but can grow into a very strong Combusken and then Blaziken. It would bring a lot of energy to Fem Ash's team and could be a great partner for her in the early stages of her Pokemon journey, especially when facing off against grass - type Pokemon.