I wonder if she is dyslexic? Has she been tested for any learning differences?
The blank look on her face, the taking so long to do her work, sounds like she is struggling.Ask the school if she can be tested and evaluated for any learning disabilities.. When was the last time her eyes were checked?
.Have you watched her writing? Have you watched her eyes as she reads? Does she read for fun? Does she write on the computer, like keep a journal or a blog?
Also once children reach this age, if they have not been taught how to study, in a way that works for them, this is the result. They become overwhelmed with the amount of work that is given to them on a daily basis.
I suggest you find an exceptional tutor, who can teach your daughter some different study habits. Yes they are different techniques for different sorts of students.