My Mother Has A High Stress Job. She Has Been

My mother has a high stress job. She has been in remission for 11 years from Acute Myeloid Leukemia. Last night she was at full body rest on the couch when she started feeling light headed and proceeded to eat a banana and some peanut butter; thinking it was low blood sugar. She was at rest and had an episode of a full body tremor while at rest. This lasted almost 5-8 mins. She felt as though she was going to pass out she was so scared. She stated she never has felt this way in her life. What could have caused this ?