For any state of altered consciousness, (fainting
, confusion, lathery, etc.), test her again. Not during a seizure
, but after she is settled, providing she is calm, and not combative. A reading that is again below the point she had felt well, proves that this low of a heart rate is simply too low for her.
Lastly, I would recommend taking her to see a Pediatric Cardiologist at an academic teaching hospital.