Frequent Fainting Spells

Our 18 year old daughter has returned home after three years in a foster home. Although she is about 20% overweight, she is taking steps to reduce her weight by dieting.  She is generally in good health, socializes well, and makes friends easily. Generally, she is creative, spry, alert, and has a good memory. She is looking forward to living at home and returning to her local high school as a senior in September 2008. About three weeks prior to  the start of school, she begain having fainting spells.  These faints last 15 - 30 minutes and usually she regains consciousness,  is able to stand up, and regains her normal thought process. She does not remember the interval of time a few minutes before fainiting, fainting itself, and the recovery cycle after fainting. Lately, she has been having 1 - 2 faints per day.

She has taken a catscan,  EKG, and EEG tests plus numerous blood tests.  None of these have indicated a neurological abnormality. They are running a thyroid test and we should have the results in a few days.  In addition, she is started taking zoloft and klonopin, prescribed by the Danbury Hospital Behavioral Health Center for Adolescents.  The medicines were prescribed about a week ago and take about two weeks to begin to work.  She will be starting a group psychological counselling program 3 afternoons a week, administered by the Behavioral Health Center.  She has been tested for epilepsy and sugar diabetes.  Both tests are negative.
Todate the Behavior Health Center has labeled her condition as "psycosomatic", which opens the door to a broad range of causes and possible solutions.
Are there any possible solutions to my daughter's fainting spells that might be considered in addition to the above?  She has never experienced fainting previously and we hope that her present coondition can be cured in the near future.Her high school is delaying allowing her to start school until the likliness of her having fainting spells is minimized.        

[justcake]

Has she had a brain MRI?   (Brain MRIs are stronger with different things than CT scans).  I would do one of those as well...

I know this isn't an easy subject to bring up, but is there any chance your daughter could be doing any drugs?  Sometimes illegal drugs can do lots of strange things to people (I'm assuming they've probably already checked her for that).

It could be just the stress of moving back home (happy stress, but still stress), and her body is having a neurological physical reaction, and it'll pass with time.

I would also be careful with the dieting--especially dieting pills.  I would just put her on a strict diet of raw fruits and vegetables with lots of nuts, with only a palm size amount of meat every day.  Strict strict strict.  No junk food, and *definitely* no sugar.  She'll lose weight this way, and be taking better care of her body at the same time.