I'm not sure. It depends on various factors and how the story was presented. Sometimes stories are based on real events but might have some fictional elements added for entertainment.
In the world of Creepypasta, Nina the Killer is smitten with Jeff the Killer. Nina has a deep - seated obsession with Jeff. She's constantly thinking about him and wants to be a part of his world. Jeff, though, is not exactly the type to have a normal loving relationship. He's a killer through and through. Their 'love story' is more of Nina's one - sided pursuit of Jeff. She sees his chaos and violence as something alluring, while Jeff may just see her as another element in the dark world he inhabits. It's a very abnormal and somewhat creepy relationship that is a hallmark of the Creepypasta genre.
Jeff is a character who has a dark backstory that led him to become a killer. In the fanfiction, he is the object of Nina's affection. Nina, she's not just a sidekick. She has her own motives and actions. She might try to change Jeff or just be with him no matter what. Their relationship and their individual personalities are what drive most of the stories in this fanfiction.
The initial key event is Nina becoming aware of Jeff the Killer's existence. This awareness sparks her abnormal love for him. As she falls deeper into her obsession, she begins to change herself. She might start wearing a similar white hoodie like Jeff, which is a very visible sign of her trying to be associated with him. Her attempts to be part of Jeff's world, by getting involved in the same kind of violent activities he does, are also important events. However, Jeff doesn't really show any real affection back. His indifference or lack of response is also an important aspect of this so - called love story, as it shows the one - sided nature of Nina's love.
One common theme is obsession. Nina is often depicted as being obsessed with Jeff, and this plays a big role in their relationship dynamics within the fanfics. Another theme is the idea of two 'broken' characters finding some sort of connection. Since they are both killers, they have a shared darkness that can either pull them together or tear them apart.
A different plotline could be set in an alternate universe where Jeff and Nina are not killers. They meet in a more normal setting, like a school or a small town. However, their dark pasts or tendencies start to surface, and they have to deal with how this affects their new - found relationship, all while trying to keep their true selves hidden from the people around them.
One common theme is the power struggle. Since both Jeff and Nina are killers, there can be a battle for dominance in the fanfic. Also, the theme of unrequited love sometimes pops up, with Nina loving Jeff but not always getting the same in return. And of course, the general horror theme of blood and gore is often there as it's part of their nature as killers.
Well, the 'nina the killer original story' might start with Nina as an ordinary person. However, she could have faced some extremely difficult situations, such as being bullied, having a family tragedy, or being exposed to some sort of violence at a young age. These experiences might have gradually warped her mind over time. As she grew older, she might have started to take revenge on those she perceived as responsible or on society in general, thus becoming a killer. But again, this is all speculation without proper knowledge of the actual story.
One good fanfic could be 'The Unlikely Bond'. It delves into how Nina and Jeff's relationship might develop in a really unique way. It shows Nina's obsession with Jeff in a more complex light, not just as a simple one - sided thing. There are also great descriptions of their interactions and how they deal with the challenges around them.