I recommend the novel, White Joy, to you. This was a modern romance novel about urban life. It told the story of the female protagonist, Bai Huanxin, who was adopted from birth. Although it was not explicitly mentioned that the female protagonist was adopted by Hades, this novel may meet your needs. I hope you like this recommendation!
You can start by giving her a distinct personality. Maybe she's shy because she's always been feared for her father's sake. Then, gradually show her growing confidence as she discovers her own strengths. For example, if she has the power to raise small skeletons as minions, at first she's scared of it, but later she learns to use it for good. Also, explore her relationships with other characters. Her friendship with Percy could be based on mutual understanding of being different among the demigods.
One idea could be a story where Hades' daughter ventures into the mortal world and has to hide her true identity while falling in love with a mortal. Another could be her going on a quest to prove herself to her father. Or perhaps a fanfic where she teams up with other mythological beings to save the underworld from a new threat.
One common theme is identity struggle. Since she's the daughter of Hades, she has to figure out where she belongs in both the wizarding world and the realm of the gods. Another theme is power and its control. Her powers from Hades are often very different from typical wizarding magic.
The other gods who don't trust Hades might be antagonists. They could see Bella as a threat because of her relation to Hades. For example, Zeus might be worried that Bella could one day try to overthrow him or cause trouble in the order of the gods.
Perhaps there's a plotline where Bella discovers some hidden powers she has as Hades' daughter. She could then use these powers to either protect the underworld or cause chaos, depending on her motives. For example, she might be able to control the souls in the underworld in a unique way that no one else can. This newfound power could attract the attention of other powerful beings, leading to various adventures and challenges.
One popular character to pair her with is Persephone. Their relationship could be explored in different ways, like a sisterly bond or a more complex dynamic. Another could be a mortal hero, creating a sort of star - crossed lovers situation. And sometimes she is paired with other underworld deities like Charon, which can lead to some really unique storylines.
One common theme is identity. Since she's Female Harry and the daughter of Hades, she often struggles to figure out who she really is in relation to both her wizarding self and her underworld heritage. Another theme is power. Her connection to Hades gives her unique powers, and stories often explore how she uses or struggles with these powers. For example, in some fanfictions, she has to learn to control her dark magic.
One great 'Female Harry, Daughter of Hades' fanfiction is 'The Underworld's Heir'. In this story, the female Harry has to navigate the complex world of being Hades' daughter while also dealing with the wizarding world. It has really interesting character development and unique plot twists. Another one is 'Shadows of the Underrealm'. Here, the author delves deep into the relationship between the female Harry and the other characters from the original series, with a dark and mysterious undertone that is really engaging.
Well, one possibility could be that Bella discovers her true parentage as Hades' daughter gradually. Maybe she starts to show powers related to the underworld, like being able to communicate with the dead or having some control over shadows. This could put her in a difficult position in the normal world of Forks as she tries to hide these new abilities from her friends and family while also trying to understand her new identity.