Well, Bella represents everything that Jacob has desired for a long time. Her presence constantly reminds Jacob of what he wants in a relationship. The imprint is something new and different that he doesn't want to accept as long as Bella is in his life. He may think that if he gives in to the imprint, he will lose his chance with Bella forever. And since Bella is constantly there, her influence on him is strong enough to make him reject the imprint.
It could also be that Jacob has his own ideals and values when it comes to love. He has this image of being with Bella in his mind, and the imprint doesn't fit into that. He might feel that his feelings for Bella are pure and true, while the imprint seems like a more primal or instinctual thing that he doesn't want to succumb to. So, in order to stay true to his own sense of self and his feelings for Bella, he rejects the imprint.
In fanfiction, Bella could hate Jacob's imprint because it represents a change that she doesn't want to accept. She might have been used to Jacob having a certain kind of love for her, and the imprint is like a sudden shift. It might also be related to the fact that the imprint might lead Jacob to be involved with someone else in a very intense way, and Bella, who has her own complex feelings for Jacob, doesn't like this new development.
Jacob's rejection of his imprint can also set off a chain reaction of events. If the imprint was seen as a solution to a certain problem in the fanfiction, such as a threat to the pack or a way to bring peace between two factions, then its rejection can make that problem worse. This forces other characters to come up with alternative solutions, and new sub - plots can emerge as a result. It can also lead to unexpected alliances as characters who previously had no connection come together to deal with the consequences of the rejection.
In many fanfictions, Bella's jealousy of Jacob's imprint can be a complex and interesting plot point. It could be because she feels left out or that Jacob has a new, strong connection. Maybe she was used to being the center of Jacob's attention and now with the imprint, she feels like she's losing her place in his life.
In fanfiction, the imprint can lead to a deeper emotional connection. Jacob may understand Bella's feelings and needs on a more profound level. He might be able to sense when she's in distress, even from a distance. This new - found closeness can also make Bella more open to Jacob, and she may start to see him in a different light, not just as a friend but as someone with a special bond to her.
Bella's jealousy might be due to envy. She sees Jacob having this intense, almost fated connection with someone else through the imprint. It makes her wonder if she could ever have such a connection with anyone. Maybe she wishes she was the one he imprinted on.
It could end with Jacob accepting Bella's decision and finding a new purpose in life outside of his feelings for her. He might move away from the area and start a new life, leaving behind the whole imprint situation.
Jacob's character often becomes more empathetic. Before the imprint, he might have been more hostile towards vampires. But after imprinting, he starts to understand them better. He also becomes more patient. The vampire he imprints on may have different ways of life or habits, and he has to be patient to make the relationship work. Moreover, he may become more of an outcast in his werewolf pack as his new relationship goes against their norms.
In some fanfictions, Jacob may reject his imprint because he has a different vision for his future. He might have dreams and goals that he believes will be hindered by the imprint. For instance, if he wants to explore the world or pursue a certain career path that he thinks the imprint will prevent. Additionally, he could be in denial about the imprint because it goes against his idea of 'true love' and he is waiting for a more 'natural' form of love to develop.
One great Jacob and Bella imprint fanfiction is 'Imprinted Hearts'. It beautifully explores the concept of imprinting in their relationship. The story delves deep into the emotions of Jacob and Bella as they navigate this new and powerful bond. Another one could be 'The Imprint's Journey' which takes the readers on an adventure with Jacob and Bella as they face various challenges together because of the imprint. And 'Imprinting Destiny' is also quite popular as it shows a different side of how the imprint affects not just them but also those around them.