A young woman was brought into the emergency room because of repeated seizures. Her roommate said that the woman had taken the drug Ecstasy the night before, and that she had been drinking a lot of water. A blood test showed her plasma Na+ was very low: 120mM (normal 135-145), and her plasma osmolality was 250mosmoles/kg (normal 280-296). Why would her low osmolality and low Na+ concentration disrupt her brain function and cause seizures? What might be a possible therapy for this person?