"surely in the case of the fork it is an obvious case of 'doesn't want to' rather than 'isn't able to'"
I'm absolutely not trying to be confrontational (because i stink at that) - but not necessarily. If DD was stomping off in a huff, I'd say this was more likely correct. But standing and staring sounds sooooo familiar to me.
I've learned with my son that very, very often, the staring indicates my instruction has kicked off a chain reaction of thoughts that he is still working through. And as a PG kid with a 94 point spread between his highest WISC subsection score and his processing speed score, I've come to understand that the chain reaction may take a while to play out.
Here is a purely hypothetical example based on the fork in the sink and my DS's seemingly wacky responses to instructions in the past:
"Mom wants me to put the fork in the dish washer. But those forks were already rinsed. Are they clean enough to put away instead? We're in a drought. It's the worst one in a hundred years. I guess it won't use more water to wash the fork with the other dishes. But maybe we should be using disposable forks so we don't have to wash them at all. Of course, then there is the landfill problem. I guess plastic is never a good answer. Even the compostable stuff sticks around for a long time. On the radio, the environmental guy said that "compostable" was mostly just for marketing, and we shouldn't use disposables ever. [NOTE: potential tangent on misleading marketing strategies DS has heard about] But then we have to use water to wash stuff. And we don't have enough water. And THAT problem is definitely getting worse. Clearly we need to figure out better desalination. But then we have to be careful about mucking with the ocean's salinity. We don't want a huge Dead Sea where the Pacific Ocean used to be. [NOTE possible thought tangent on what caused the Dead Sea to die] But maybe we could cycle the water back into the ocean. I think I have a book about the water cycle under my bed. [walking away to get book]. 'Mom - why are you yelling at me? Oh - the fork. Sorry.'"
As I've wondered about in other threads - I'm not convinced that the lower measured processing speed for these PG kids is actually a function solely of SPEED. Rather, it's at least heavily influenced by VOLUME of what is being processed. To put it another way - an absent-minded professor isn't really absent. He's just present in many other places than where we want him AT THAT MOMENT.
On a more practical level - when I spot this happening with my DS, I feed him an appropriate verbal response. I'll say "Now you say to me, 'OK Mom, I'll put the fork in the dish washer.'" Very often, he will parrot the response, and then realize that means he was supposed to be doing something. I won't say he always does it (see stomping off in a huff comment above). But at least we are both on the same track at that point.
And on a slightly heartbreaking point - he has often sobbed about the fact that nobody believes him when he says he really wasn't ignoring instructions. He just couldn't get to them.
Hope you can find a strategy that helps with your daughter. But I really wouldn't start with the assumption that she's being willfully naughty. We learned the hard way that assumption - and the discipline strategies that flow from it - only make the problem worse. because the strategies aren't really addressing the problem. They're just punishing the kid for something they don't know how to change.
Sue