So, this could just be me projecting, but I've long suspected that Kaede comes off like an undiagnosed ADHD kid. [snip]
While she may have ADHD, I do not think it is a necessary precondition to her having poor impulse control. Even a neurotypical person who did not receive enough positive socializing early in life (e.g. because she is too busy reading and drawing manga) can have difficulties managing her emotions effectively, without either doing whatever she feels like in the moment or suppressing them outright (which only leads to extreme outbursts). I think that this is what happened to Kaede, and that this isn't all bad: the fact that she preserved her genuine child-like enthusiasm for things is, as you've observed yourself, makes her so attractive to caretaker figures in her life. At the same time, however, this also allowed her to effectively free-load off them her whole life without having to confront the downsides of her impulsivity. Kaede thinks that being an adult is earning a living wage, while in reality, it is much more about learning to strike balance between feeling all of her feels and still doing what's best for her and for people around her in the mid-to-long term.