My 8 year old was recently assessed by a clinical psychologist as being highly gifted, as a result of having her evaluated for ADHD at her school's request (which she doesn't have). He also said that she has trouble processing information, which is why she appeared to always be distracted.
Did he give you specific information on how to work on her processing problems? I would venture to guess that if you resolved/worked around the processing issues you would "see" more of her giftedness. I'm going to go out on a limb and guess that the ADHD the teachers see is really her acting out due to currently not being in an appropriate educational setting for her level of giftedness.
ETA: Being gifted does not necessarily translate to being highly motivated. Especially if she's been in a traditional classroom for the past 3 years. Not all gifted students have the same level of motivation. Plus, if her processing problem is causing her to have to expend extra energy to get her work done, she's not likely to want to spend even more time putting in all that extra effort.
