Hi, I'm 17 and a senior in high school, so I thought I might be able to help. Actually, as I was reading your post, I noticed that I have a lot in common with your daughter.

I was diagnosed with ADD when I was a sophomore in high school, after a rather tumultuous year in school. I can definitely relate to the mind never stopping thing. That is one of hte major problems that I have had that caused me to seek help. It's like there are so many things going on in my head and at such a fast speed, that it is overwhelming. I used to come home exhausted every day from school, just from thinking so hard. I also have a constant monologue going on in my head, kind of like a really fast paced commentary on the world around me. It is very frustrating. I was also very shy as a child, and I have always felt that I didn't want to grow up- I think I have said that very thing, that I wanted to be 5 years old again.
Also, just a thought- while the symptoms must be present before the age of seven, it may not cause significant problems until later in life. In my case, I was able to compensate for my very poor organizational skills and inattention because I had very supportive parents and was never any trouble behaviorally in school. I was very quiet and compliant, and I worked hard, so I managed to do fairly well until the work became a lot more complex. However, my self-esteem and confidence suffered a lot, although at the time I didn't know why. It wasn't until I started researching the disorder that I realized how it had affected all aspects of my life. So anyway, I would consider getting it checked out.
Another thought- while I was being tested, the psychologist had some difficulty differentiating between ADD and anxiety, because the symptoms overlap.I was also somewhat depressed, which can also cause these symptoms. So it is important to not rule out these possibilities. However, in my case it was decided that the anxiety and depression were a result of the ADD, not the other way around.
It sounds like you are doing the right thing- a counselor is a good person to start sorting these things out. That is how it all started for me- and it seems I was facing many of the same difficulties as your daughter. I hope I have helped in some way. Good luck to you and your daughter.