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.
Yes, there are likely such fanfictions out there. Fanfiction platforms host a wide variety of stories based on different interpretations of characters and relationships. However, these often deviate from the original story's canon.
Edward might be initially shocked and heartbroken. He has been in love with Bella for a long time, so her leaving for Jasper would be a huge blow. He could become withdrawn and moody, brooding over what went wrong.
One common theme is the exploration of love triangles. Since Edward, Jasper, and Bella are all in an interesting dynamic, many fanfictions focus on how their relationships could be reimagined in different ways regarding love and attraction.
The theme of self - discovery for Bella is also common. In these fanfictions, being around Edward and Jasper often makes Bella question who she is, what she wants in life, and how she fits into the vampire - human world. For example, she may discover new aspects of her personality or hidden powers as she gets closer to them.
One common theme is the exploration of complex relationships. Since it involves Bella, Edward, and Jasper, there are always different dynamics at play. Love triangles are also a very common theme. Another theme is the supernatural aspect, given that they are from the Twilight universe which has vampires and other supernatural elements.
One common theme is the love triangle. The complex relationship between Jasper, Bella, and Edward forms the core of many stories. There's often a struggle for Bella's affection between Edward's intense love and Jasper's more reserved yet deep - seated feelings.
There might be a fanfiction titled 'Edward, Jasper and Bella: A New Beginning'. In this, perhaps they start a new life away from the typical vampire - human - vampire drama of Forks. They could be in a new location, building new relationships and exploring different aspects of their characters.
In such fanfictions, a recurring theme is the disruption of the established order. The Twilight series has a set relationship dynamic, and when Bella cheats with Jasper, it shakes things up. There might also be themes related to the consequences of one's actions. Bella would have to face the fallout from her decision, not only with Edward but also within the larger vampire - human community in the story. Plus, themes of love triangles and internal emotional battles within Bella as she tries to navigate her feelings for both Edward and Jasper are likely to be present.
One key element is the shift in power dynamics. Usually in the original Twilight story, Edward has a lot of control over Bella. In these fanfictions, Jasper disrupts that by saving Bella, which changes the whole dynamic. For example, Bella might become more independent.