This is AU to the Descendants books; I am basically using the Mal character and putting her into the Kingdom Hearts universe.
Mal was the teenage daughter of Maleficent and Hades, raised by her mother to be her heir for the title of the Mistress of All Evil. She was the result of a fling between her parents when her mother was starting to lay the groundwork for her plans to engulf all worlds into darkness and to find Kingdom Hearts to reshape the universe in her image.
Things had ended badly for their relationship and so after she was born; her parents acted more like unwilling co-workers to eachother than exes. She was born Maleficent Jr but her mother didn't think she was evil or powerful enough to deserve to go by her full name yet.
She was raised by her mother to be as bad as possible; but after her infancy it was mostly her main henchman Pete raising her while she worked on her plans to engulf all the worlds. She was not allowed to help and was encouraged to stay as far away from the plans and her associates as possible.
She knew that her mother didn't trust her to be able to pull off any tasks that she was given. She always hated not being good enough for her mother but did her best not to visibly or verbally show it, any form of weakness shown by her would not be tolerated by her mother and would be punished.
In Hollow Bastion she stayed away from her mother and her little council of allies as they hatched their schemes, she saw her mother bring in a boy called Riku who she was manipulating into being her servant. She spied on their interactions and Maleficent had said he was like a son to her.
It was all false but Mal did her best to hide tears; the false affection shown to Riku was more affection than she had ever been given.
She was in her room but found the door being opened and saw the new Key Bearer, a boy her age called Sora. Of course he didn't have his Keyblade at this point as the Riku boy had taken it from him. They were both startled and Sora apologised and introduced himself to Mal.
"I'm Mal, Maleficent's daughter." Mal introduced feeling like she didn't want to put any effort into hiding who she was. Sora was surprised but looked at how sad Mal seemed to be with her demeanour.
He asked if she was okay and Mal was startled when she saw that Sora seemed genuine in his concern. She told him that she was fine and decided that she wanted to do something that could threaten her mother's plan, even if how small.
Nothing she ever did was good enough for her so why bother try to help her, she could easily have the boy restrained right now but she doubted even that could earn her any actual praise.
She then told Sora the best directions of the castle to get to her mother and the Riku boy.
Sora gave her a smile and thanked her before going off with Mal surprised he accepted it so very easily. Not even a brief questioning of why he should trust her or thinking she was leading him into a trap. Either he was an idiot or stupidly naive. Probably a goody good who wanted to see the best in everyone.
It seemed charming to her.
Sora ended up getting his Keyblade back and locked Kingdom Hearts, after slaying her mother in dragon form. Mal tried to be more upset about this than she actually was. She tried not to feel relief but knew her mother could return. When Mal was a toddler, her mother had been killed before; by the teamwork of another Key bearer called Aqua and a prince called Phillip. However she had returned after that.
She once found her mother explaining to a servant that she had become so powerful that she could always return after death for as long as people are able to remember her. It always seemed like it would happen because she had definitely built up a reputation as the Mistress of All Evil.
After the worlds returned to normal and Hollow Bastion turned into the Radiant Garden, she settled a new life there. Thanks to the teachings of her mother, she could not help but try to be as bad as she could.
However it just amounted to mischievous pranks and being a little bit off a troublemaker and the people didn't seem to mind too much; okay they would glare at her at her antics but she was viewed as just a prankster than just rotten to the core.
It didn't bother her as much as it had before because she managed to build a new life there. One day she found Sora coming back there with his Keyblade on a new adventure going against a group calling themselves Organisation XIII.
"Wonder how many of them they are?" Mal had snarked upon hearing the name.
Sora spent some time with her apologising about what he had done to her mother but Mal said it was fine. Mal admitted she was taken aback by how cheerful Sora was and how he didn't hold her mother's crimes against her. It seemed her suspicions of him being a goody good were spot on.
While she thought his attitude and demeanour was silly, she found it charmingly silly. After spending most of her life around evil people she found it nice to be around good and nice people. She found Sora's company to be great and how she finally had a real friend.
After some time where he visited even after beating the Organisation, she began thinking of Sora as more of a friend. Once she had thought about her feelings she decided that she didn't want Sora as a friend who was a boy but as a boyfriend.
One thing she had in common with her mother was that they were proactive in going after what they wanted.
She decided she would start flirting with him, of course with how much of a clueless person he could be she would have to wait a while before he would get the hint that she was flirting with her. If she runs out of patience with his denseness she could try just flat out admitting she likes him and asks him out.
She knew her mother would not be happy with her but what else was new?