Well, it could make James more protective of his remaining family and friends. He might become more serious and less carefree, as the loss of a sister is a huge blow. It could also fuel his determination to fight against whatever forces caused her death, like in the wizarding world, it might be dark wizards or some sort of magical curse.
One great fanfiction about James Potter's little sister is 'The Potter Sibling Bond' on FanFiction.net. It delves deep into her relationship with James and how she copes with the family legacy. It has a really engaging plot that keeps you hooked from start to finish.
One common trope is the overprotective James. He's always looking out for his little sister and getting into trouble when someone messes with her. For example, in many fanfics, if someone teases her, James is quick to hex them. Another trope is the sister having a special power that no one else in the family has, like being able to communicate with magical creatures in a unique way.
She might be a bit intimidated by them at first. Since James' friends are known for their mischief and popularity. But as time goes on, she could become friends with them too. For example, Sirius might take her under his wing like a little sister as well, teaching her some of his prank - pulling tricks.
One possible storyline could be that James Potter's little sister is a bit of an outcast in the wizarding world because she doesn't have the same brash and popular personality as James. Maybe she's more into books and research. She could struggle to find her place among the Gryffindors who idolize her brother. Another could be that she has a special power that she's afraid to show because she doesn't want to be compared to James all the time. And she might form an unlikely friendship with someone from a different house, like a Ravenclaw, who helps her explore her own identity away from her brother's shadow.
One day, James Charles' little sister decided to follow in her brother's footsteps in the world of makeup. She started by borrowing his makeup brushes. With a determined look, she began to apply bright eyeshadow, just like she had seen James do countless times. But being younger, her hand wasn't as steady, and the result was a bit of a colorful mess. However, James saw her effort and instead of laughing, he gave her some tips on how to hold the brush properly and blend the colors better.
One common theme is family. Since she's James Potter's sister, there's often exploration of her relationship with James, their parents, and the rest of the family. Another theme is identity. She has to figure out who she is within the shadow of her famous brother. For example, in some fanfics, she might struggle to find her own place in Hogwarts or in the wizarding world in general.
She might have been lured into a trap by a dark wizard who was after the Potter family. The dark wizard could have used her as a bait to get to James or his parents. Another way could be that she was suffering from a mysterious magical illness that couldn't be cured in time. This would add a sense of helplessness to the situation as everyone around her tried their best but still couldn't save her. It could also be that she got lost in a dangerous magical place like the Forbidden Forest and couldn't find her way out, ultimately meeting her end there.
One common theme is family. Since she's James Potter's sister, her relationship with her family, especially James, is often explored. It could be about how they support each other or have sibling rivalries. Another theme is identity. She has to figure out who she is in the shadow of her famous brother. For instance, in some fanfictions, she tries to make a name for herself independent of the Potter name.
Friendship is also a big theme. She forms her own group of friends at Hogwarts and these relationships help shape her character. In some fanfictions, there's a theme of rivalry too. Not in a negative way always, but a friendly rivalry with James or other students in terms of magical achievements. These themes all come together to create an interesting and complex story.