...I dunno... Reading the report, there are more than just seizure in the symptoms:

- 13:00 felt "weird" and had a headache
- started to become confused, then unable to speak
- soon started stumbling, and could not stand up
- patient had a full body seizure while being carried
- 22:15 patient was responsive to painful stimuli only
- appeared to be in a stupor,
- unable to speak or follow commands
- She vomited

From Mayo Clinic site:
Hyponatremia signs and symptoms may include:

- Nausea and vomiting
- Headache
- Confusion
- Loss of energy and fatigue
- Restlessness and irritability
- Muscle weakness, spasms or cramps
- Seizures
- Coma

The way her symptoms progressed, in my mind, they point toward hyponatremia or altitude-induced cerebral edema. What is missing in the report is how much water she was consuming and whether she was getting any electrolytes with the water.

I would sure like to see the diagnosis.