Also remember she is only eight.
Think hard about what you, yourself, consider success. If it is becoming a well adjusted adult, ready to play a constructive role in society, that is fine. Support her with weaknesses, but allow her to feel pride in things she is good at.
When looking at secondary schools, consider those where credit and status is given to both academic and non academic achievements. Consider co-ed, as more boys seem to have an uneven profile, so if she ends up bouncing along the bottom in English, she won't be alone.
The key thing is that it is fine for her to be clever but not academic, if that is what she is. There are plenty of people like that. DD recently described a friend who is skipping University to do an apprenticeship as "clever, but not school clever". And indeed with his range of social and emotional skills, it's more than possible that this boy will do better than many of his university educated peers.
That said support her, as you want to keep as many doors open as possible. Plus kids who don't fit standard profiles can get lost. We, and DD, were genuinely surprised when she suddenly took off academically at around 14. I think it was at the point when some of the diligent kids, who had previously come top of the year, were struggling with maths and science concepts. But even if she had not, it would not have mattered. She had a good range of non academic interests and talents she could have pursued.
I don't know what you do about the disorganisation. Its gets better over time, but DD still seems to need more support than her brother did at the same age.