Well, one possibility could be that Rey, through some sort of time - bending Force power, is transported to a time when Anakin was still a young Jedi. They could meet on a mission to a far - flung planet. Rey, with her knowledge of the future, tries to subtly guide Anakin away from the dark side without revealing too much.
A Sith Lord who has been manipulating events from the shadows could be the antagonist. This Sith Lord might be trying to use Rey's connection to Anakin to bring about the return of the Sith in a new and more powerful way. He could be using dark side illusions to make Rey and Anakin distrust each other.
Well, Anakin is from an earlier era in the Star Wars universe and Rey is from a later one. If they were to meet, Anakin could perhaps see the potential in Rey and offer to train her in the ways of the Force, just like he was trained. He might be impressed by her natural abilities and her strong connection to the Force that she has already shown.
In a fanfiction where Rey meets Anakin, one possibility is that Anakin would see Rey as a symbol of hope for the future of the Jedi. He might take it upon himself to train her in the ways of the Force more deeply, sharing his own experiences both good and bad. Maybe he would guide her in how to avoid the dark side's temptations that he himself succumbed to.
Yes, in some fanfictions, Rey is considered as Anakin's reincarnation. This idea often stems from the strong connection to the Force that both characters possess. There are fanfic writers who like to explore the concept of a spiritual or karmic cycle in the Star Wars universe, and this reincarnation theory is part of that exploration.
Anakin could be angry. He might see his other self as a threat, especially if one represents his dark side and the other his light side. There could be a power struggle between the two versions of himself as they try to assert dominance over the other. Or he could be curious and eager to learn from his other self, about what he could have been or what he can still become.
If Anakin meets Rey in fanfiction, they could talk about their destinies. Anakin was believed to be the Chosen One, destined to bring balance to the Force. Rey is also seen as a very important figure in the new era of the Star Wars universe. They could debate what it really means to be 'chosen' and what responsibilities come with it. Anakin could warn Rey about the potential pitfalls of having such a big destiny, like the pressure it can put on a person and how it can lead to making wrong decisions if not careful.
In this fanfiction, the plot could revolve around Rey being haunted by Anakin's presence in the Force. She starts to have dreams where he shows her different scenarios of his life. As she delves deeper into these visions, she uncovers a conspiracy within the Jedi Order that was related to Anakin's downfall. Rey then uses this knowledge to reform the Jedi in the present day, all while being inspired by Anakin's complex story.
One way to write it could be by having Rey discover old holocrons about Anakin. She could be in awe of his skills as a pilot and Jedi. She might start to mimic his fighting style and try to understand his fall to the dark side and subsequent redemption. This would create an interesting dynamic as she tries to learn from his journey.
I really like the fanfic 'Anakin's Guidance for Rey'. In this story, Anakin, as a Force ghost, appears to Rey after she has started her Jedi training. He gives her advice on how to deal with the dark side of the Force, based on his own experiences. It has a lot of great dialogue and shows how Anakin has grown in his understanding of the Force even after his death.