Symptoms of concussion:
http://www.nlm.nih.gov/medlineplus/ency/article/000799.htmIf any of these signs are present, immediately call your health care provider.
Emergency signs:
Persistent unconsciousness (coma)
Altered level of consciousness (drowsy, hard to arouse, or similar changes)
Persistent confusion
Convulsions
Repeated vomiting
Unequal pupils
Unusual eye movements
Muscle weakness on one or both sides
Walking problems
Hopefully you've mentioned this passing out thing (Vasovagal syncope) to her ped. doc.?

Sometimes it can be a symptom of heart disease, and some forms of heart disease are hereditary (my Mom has a rare one called Prinzmetal angina, for example, which has caused sudden death in three generations of her family-my Great-Aunt Rose died while lifting her breakfast coffee cup to her lips. My Uncle always says,
at least she could've had her coffee first

)
More on Vasovagal syncope:
http://www.cnn.com/HEALTH/library/DS/00806.html