Can Migraine Cause Fainting?

Hi, my mother is 47 years old, and has never had a history of fainting. 2 years ago, she passed out during a lunch break at work. Nothing was ever diagnosed from it. Now today, she was shopping, and she said she felt it "coming on" and fainted again, but this time the EMT said she was foaming at the mouth also. She is a frequent sufferer of migraines. What could this be?