In addition to the neuropsychologist testing, please have her evaluated for sensory issues. Sometimes a child's body (or adult's) does not handle input from the senses in the best way. This can cause them to seek or avoid certain types of sensory stimulation. Her only speaking in a yell, for example, may be because her brain is telling her she needs the loud noise.
There are a LOT of things that can help sensory issues but it all starts with a thorough evaluation by an Occupational Therapist. Schools have them, but I STRONGLY recommend that you have a private evaluation done also. Why? School OTs look for what is impacting her at school, while a private Occupational Therapist (OT) looks at her entire life, not just her time at school.
As an adult with sensory issues, who can remember having them from my earliest memories, I beg you to get help for her. It can be nearly impossible to ignore something that is major to you but seems so incredibly minor to others. If I have a scratchy tag in a shirt, I literally cannot function. If my clothes itch, the day is over until I am out of them. I literally am UNABLE to think and I can cope with exactly NOTHING, not even things that I would normally not even notice. My brain is incapable of overlooking or ignoring the sensations. The longer I try, the harder it becomes to cope. This is what it is like for me, an over-40 yo mother of 3. Imagine how much harder it is for a child who has no idea why she feels like this or what to do about it?
You can learn more about sensory issues in "The Out of Sync Child" by Kranowitz.
sensory issues CAN be helped. One way is to provide a sensory diet of the types of sensations her brain and body crave, and this is important as it gives her a way to cope. Another method is called brushing. it uses a super soft brush to go over the body a certain way in order to retrain how the brain gets sensory input. I thought it was hocus pocus until I saw it work. It truly is astounding and it is medication free and very safe. You must be trained by an Occupational Therapist (OT) and then you do this with your child at home. This has the added benefit of making it inexpensive too (always a plus, in my opinion! esp given the cost of so many things to help our kids). By watching my youngest son for signs of sensory overload, using the right sensory diet for him, and brushing, my son went from missing most of the school week due to being totally overloaded to missing 1-2 days an entire year in just a couple of years. He was an extreme case and would go into a state of sensory overload that most kids don't.
I hoep this helps and that the various books we have suggested help. I also strongly suggest "What your Explosive Child is Trying to Tell You" and "Parenting Your Child with Love & Logic"