I Am Looking For Information On Food Coma. My Friend

I am looking for information on food coma. My friend has an almost "high" reaction to any meal with even just a few carbs in it. She has been tested for diabetes and it is negative. Last night's meal was Homemade biscuits and sausage gravy, with a side of bacon. Half an hour later, she was unable to function her eyes were reddened and her speech slurred. Blood sugar read at 138.