She could be on a quest to clear her father's name. Since Sirius was wrongly accused of many things, she might dig into the past, find evidence that he was innocent all along. For instance, she could discover hidden letters or witnesses that were overlooked. This would lead her into many dangerous situations as there are those who would rather keep the truth buried.
One possible plot could be that Harry discovers the truth about her real parentage early on. She then has to deal with the implications of being Sirius' daughter while still at Hogwarts, facing both the admiration and suspicion from others.
She could also be an innovator. She might come up with new spells or magical techniques. Since she has the blood of Sirius Black in her, she could be a natural at magic and use her creativity to solve problems that Harry and his friends face, like finding a new way to combat the Dementors or a more effective way to pass their exams without the use of cheating spells.
There probably is. The Harry Potter fandom is huge and full of diverse ideas. Writers might explore this idea to add new twists to the story, like how Harry's relationship with Sirius would be re - imagined if he were his daughter, and how it would change the overall plot dynamics.
The plot could involve Petunia using her witch powers to protect Harry from the Dursleys' abuse. She realizes that she has a responsibility towards her sister's son and uses her magic to create a safe haven for him within the Dursley household. This would be a big change from her original character who was so against magic.
Perhaps Fleur Delacour's sister is an exchange student from Beauxbatons to Hogwarts for a special program. She arrives with high expectations but is met with some resistance from the Hogwarts students who are a bit jealous of her connection to Fleur. However, she quickly proves herself by being extremely talented in a different area of magic, like potion - making. She then enters the Triwizard Tournament as an honorary contestant (due to some special rule) and has to face various challenges, all while trying to make friends and fit in at Hogwarts.
One interesting fanfiction could be about Sirius Black's daughter joining Harry Potter and his friends on their adventures at Hogwarts. She might inherit her father's brave and rebellious spirit, causing some interesting twists in the story.
One possible fanfiction could be about Sirius Black's daughter discovering her father's true nature and his relationship with Harry Potter. She might start at Hogwarts and face some challenges due to her father's reputation. For example, some students might be wary of her at first, but she gradually proves herself to be a brave and kind witch, just like her father.
I'd suggest 'Remus Lupin's Secret and Sirius Black's Redemption'. This fanfic focuses on the secrets that Remus has been keeping and how Sirius helps him come to terms with them. It also delves into Sirius's journey of redemption after his time in Azkaban. It's a heart - wrenching and yet heart - warming story.
She could be kidnapped by a group of rogue vampires who think they can use her to gain leverage over the headmaster. Her friends, both human and vampire, would then have to team up to rescue her. During her captivity, she might learn some secrets about the vampires that could change the way she views them.
Perhaps Sirius Black's daughter has a special connection to Harry through a long - forgotten prophecy. They start to notice strange coincidences and shared dreams. As they investigate, they find out that their destinies are intertwined in a way that could change the wizarding world. It could involve a journey to find a lost magical artifact that holds the key to fulfilling the prophecy.