My mum became unresponsive and sat rigid after eating dinner at a restuarant.? My mum and dad live in Canada and my sister went out to visit them. One night they decided to have dinner, after dinner my sister was talking to my mum, when suddenly she said she wasn't feeling well and felt faint. The next minute, she became totally unresponsive, her eyes flickered and her body was totally rigid. My dad kept trying to talk to her, but she was totally unresponsive for about 2 minutes. Then my sister laid her down and she was okay and tried to sit up. When she sat up it happened again, then my sister made her lay down again and she was okay again. My sister made her go to the hospital and they said that she had dangerously low blood pressure, they couldn't find anything else wrong with her. What could be the cause of this and what would the treatment be? Please only give helpful answers as I am really worried about her.

Summarized question: What causes unresponsiveness with low blood pressure?