Whenever a child experiences a sudden illness, especially loss of
consciousness, it is important to seek medical advice as soon as
possible. It is possible that her fainting spells are caused by
something as simple as dehydration, but the fact that they are
accompanied by nausea and vomiting could indicate a more serious
cause. Your pediatrician will be able to perform a few tests
(including possibly a "tilt-table test") to determine possible causes
for her fainting.
I went to MEDLINEplus, the consumer health resource from the National
Library of Medicine, to find some information for you. I think the
following quotation from the Mayo Clinic sums up the feelings of us
Researchers about your case:
"Fainting occurs when the blood supply to your brain is momentarily
inadequate, causing you to lose consciousness. Loss of consciousness
is usually brief.
Fainting can have no medical significance, or it can be caused by a
serious disorder. Therefore, treat loss of consciousness as a medical
emergency until the symptoms are relieved and the cause is known."
I would suggest that, after you schedule an appointment with your
doctor, you take a look at some of the resources available in the
health topic for "Fainting" (or syncope, as it is called technically)
in MEDLINEplus: http://www.nlm.nih.gov/medlineplus/fainting.html.
I think you will also find the encyclopedia article in MEDLINEplus
Again, please heed the warning of the Mayo Clinic and other resources
given above, and treat this as a medical emergency. Call your
daughter's pediatrician, the local pediatric clinic, or even the
emergency room to get help.
Best of luck, please don't hesitate to clarify if you need more