Suggest Remedy For Migraines

My sister was giving plasma then fell on the floor, was curled up in the fetal position (involuntarily), hands curled, mouth wide open, almost seizure like, couldn t talk or move, only tears streaming down her cheeks. After about 3 minutes she finally came to and said she could feel the whole thing and remembered it all, just couldn t move and her whole body just curled . She started crying as she was scared. She felt trapped in her own body. Any thought of why this would happen or what caused it? Maybe a seperate issue just triggered? The ER couldn t find anything wrong. She s been having migraines since and has never had migraines previously.