For writing her character, you need to think about her place in the wizarding world. She's the daughter of a controversial figure. So, she might be constantly in the spotlight. This could make her either shy away from attention or use it to her advantage. Her magical abilities should also be developed in a way that makes sense. Maybe she has a natural aptitude for some spells that Snape was also good at, but she struggles with others. Her relationship with her peers is crucial too. She could be a bit of an outcast at first, but as the story progresses, she forms deep bonds. You can also explore her emotions towards her father's death and how it affects her growth as a witch.
In these fanfictions, Snape often becomes more self - reflective. He starts to realize the full extent of his actions and how they've affected others. For example, he might come to see how his treatment of Harry was unfair. He also becomes more open about his emotions, which was something he always hid before.
Her presence could also make Severus more vulnerable. He might be more likely to show his emotions and softer side. In the fanfiction, she could be the only person he truly trusts. So, when she gives advice or asks him for help, he would act accordingly. This could change his actions towards his students, his colleagues, and his role as a spy. For example, he might be more lenient with students if his sister has a positive view on nurturing young witches and wizards.
In some fanfictions, Severus Snape's character develops by becoming more open - minded towards Muggles. He might start off with his typical wizarding - world prejudices, but through various interactions, he begins to see Muggles in a new light. For example, he could meet a Muggle scientist whose thirst for knowledge reminds him of his own love for potions, and this changes his view.
She would likely be very intelligent. Snape was a brilliant wizard, and he would surely pass on his knowledge and love for learning. She might also be a bit reserved and guarded, just like her father. His experiences made him cautious, and she could inherit that trait. And she'd probably have a strong sense of loyalty, especially towards those she cares about, as Snape was ultimately loyal to Dumbledore and the cause of good.
Snape's character changes in his relationship with others too. He becomes more involved with the Hogwarts community as he is now responsible for Harry. He might start to collaborate more with other teachers, like McGonagall, who he previously had a rather cold relationship with. His attitude towards the students also changes as he realizes that they are just kids trying to find their way, much like Harry. This is a big shift from his usual strict and often unforgiving self.
Snape's character could become more complex. He might start to incorporate some of Merlin's wisdom into his own actions. For example, Merlin was known for his ability to see the good in people, and Snape could start to do the same. Instead of just being bitter and resentful towards Harry, he could start to see Harry as a potential ally in a greater fight, much like Merlin saw the potential in the young knights of Camelot.
Snape's character often becomes more open - minded. In many such fanfictions, being around the Marauders, who are generally more carefree and adventurous, forces Snape out of his shell. He starts to see things from different perspectives, rather than just being the brooding loner he was originally.
One great Severus Snape daughter fanfiction is 'The Snape Legacy'. In this story, his daughter has to navigate the complex world of Hogwarts while carrying the weight of her father's reputation. It shows her growth from a shy girl to a powerful witch, with interesting plot twists involving her relationships with other students and teachers.
The re - imagining of Snape as trans in fanfiction can also play with the idea of how magic could interact with his gender identity. For instance, could there be spells or potions that are more difficult for him to use because of his trans identity? Or perhaps there are magical ways to help him transition that are unique to the wizarding world. His role as a Potions master could also be tied into this, like creating new potions related to gender transition or using his knowledge to help other trans wizards in the fic.
One common theme is identity. Since she is Snape's daughter, she often struggles with defining herself apart from her father's complex legacy. Another theme is acceptance, both from the Hogwarts community and within her own family. For example, in many fanfics, she has to prove herself worthy to be in Slytherin like her father.