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she had would have resulted from CNS (Central nervous system
+ Brain and spinal cord
) or from Heart problems.
The tests you have done do rule out CNS causes to maximum extent but i suggest you also get her heart checked by getting a ECG ,2D Echogardiography and a carotid Doppler these tests will make sure the normal functioning of the heart also get her blood pressure checked repeatedly at different times for 3 to 4 days and consult the cardiologist with the reports.
Also keep her energy levels good with juices and regular food and have a good watch on her for safety and symptom witnessing.
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