Maybe she was a serial killer. She could have been luring people into her house and then harming them.
It could be that she was haunted herself and the 'horror' was that whatever was haunting her started affecting the neighbors too. For example, they might start seeing strange apparitions or experiencing unexplained cold spots, all because of her connection to the otherworldly. And this all stemmed from her living right next door, making it a truly terrifying situation for those around her.
She might have been involved in illegal and dangerous experiments. Picture this, strange lights and sounds coming from her house at odd hours. And then, people in the neighborhood start getting sick, and it's later found out that she was doing some sort of chemical or biological experiments that were not only illegal but also extremely hazardous, creating a horror - filled situation for everyone nearby.
One possible plotline could be that the girl next door has a health scare and decides to build muscle as a way to improve her overall health. She starts going to the gym regularly and slowly but surely builds her strength.
One possible theme is growth. The girl next door could grow from a shy, introverted person to a confident individual. Another theme might be community. She could play an important role in bringing the neighborhood together, like organizing block parties.
One possible theme could be friendship. Since it's about the girl next door, it might focus on the bond that developed between the protagonist and the girl.
Social stigma is also a major problem. People in the neighborhood or at school/work might be judgmental or discriminatory. She could face bullying or exclusion. And also, accessing proper medical care for her transition, like hormone therapy, can be difficult due to various reasons such as cost and lack of understanding from some medical providers.
The main character is likely the person telling the story, who has an interest in the girl next door. The girl next door is a central character too. She might be portrayed as having unique hobbies or characteristics. There could also be the girl's family members, such as her parents or siblings, who may influence her actions or the relationship with the narrator.
Another theme might be self - discovery. The girl could be on a journey to find out who she really is, perhaps trying different things and learning more about her own values and dreams. She might start out as a shy girl but through various encounters, she discovers her hidden strengths and capabilities. This could be a central theme in the story as it shows her growth and development.
One possible theme could be deception. The girl next door seems normal but is hiding something horrible.
One interpretation could be a story about a girl who lives next to someone and they form an unexpected friendship. For instance, she might be from a different background, but through daily interactions, they get to know each other better.
Another theme might be the breakdown of trust in a community. When a crime happens to the girl next door, neighbors start to question their safety and the safety of those around them. It also could be about the search for justice. The story may focus on the efforts to find the perpetrator and make them pay for their crime, showing the importance of the justice system in such cases.
One possible theme could be friendship. Since it's about a girl next door, she might have formed strong friendships in the neighborhood in 1998. Another theme could be family, if her family played a role in the events of the story.