One possible reason could be that Paul represents a different kind of life for Bella. Maybe he is more down - to - earth compared to the often brooding Edward. Paul might offer a simpler and more straightforward relationship without all the supernatural drama that comes with Edward.
It could also be that Bella feels a stronger emotional or physical connection with Paul. Their personalities might mesh in a way that makes her realize her relationship with Edward was not as fulfilling as she once thought. Paul might be more in tune with Bella's immediate needs and desires, rather than Edward who is often preoccupied with his own vampire - related issues.
Edward might be initially shocked. He has always seen Bella as his own and this sudden change could be hard for him to accept. He could become withdrawn and moody, similar to how he was before Bella entered his life.
One possible reason could be that Bella discovers a different side of Jasper that she finds more appealing. Maybe Jasper shows a deeper understanding of her in some aspects that Edward lacks. For example, Jasper's past experiences might make him more empathetic towards Bella's own struggles in a way that Edward, with his own set of vampire characteristics, doesn't quite get.
It could be that there are external forces at play. Maybe there are other characters or some kind of dark secret in the fanfiction lore that forces Edward to leave Bella while she's pregnant. For example, there could be a threat from a rival group that says they'll harm Bella and the baby if Edward stays, and he thinks leaving will draw the danger away from them.
One possible reason could be that Bella discovers a side of Rosalie that she feels more connected to on an emotional level. Maybe Rosalie shows her a different perspective on the vampire world that Edward had been hiding from her. Another aspect could be that Bella has grown tired of Edward's over - protective nature and sees Rosalie as a more independent and free - spirited vampire to be around.
I'm not sure if there is a particularly popular one. Fanfiction varies greatly in popularity and it depends on different fan communities. Some fanfictions might gain a following in certain groups who enjoy exploring alternative storylines, but it's hard to say for sure without extensive research into the Twilight fanfiction world.
Well, it could be that Bella decides to raise the baby on her own without Paul. She could focus on building a support network of friends and family. Another aspect could be that the werewolf or vampire community (depending on the context of the original story) has some sort of reaction to Bella's situation. For example, they might try to protect her from any threats that come her way because of the unborn child.
It could also be due to misunderstandings. Fanfiction often plays with the idea of miscommunication between them. Maybe Bella misinterprets Edward's over - protectiveness as a lack of trust in her ability to handle vampire - related situations. Or Edward might misunderstand Bella's need for independence as a sign that she doesn't love him as much as he thought. These misunderstandings can escalate into arguments.
One possible plot could be that Edward, perhaps influenced by some dark magic or a misunderstanding, decides he has more in common with Harry. Maybe he sees Harry's courage and selflessness and feels drawn to that world. He leaves Bella heartbroken, and Bella then has to find a way to move on while Edward starts a new life in the wizarding world with Harry as his new friend or more.
The reaction of Twilight fans would vary widely. On one hand, die - hard fans of the Bella - Edward relationship would probably be horrified and might even condemn the fanfiction. They've invested a lot of emotion into the original pairing. On the other hand, there are fans who are more into alternative or 'what - if' scenarios. These fans might find it fascinating to see how the story could play out if Bella cheated on Edward with Paul. Additionally, some fans who are just into exploring different character interactions might also be intrigued, but overall, it's likely to cause a lot of controversy within the fan community.
Maybe the writer of the fanfiction didn't capture the essence of Paul's character accurately. Paul might be written in a way that is out of character, such as making him act too harshly or without proper motivation towards Bella. This could lead to a scenario where the idea of 'paul rejects bella' seems forced and not in line with what fans expect of the characters.