My Brothers Girlfriend Has Been Having Episodes At Least 20

My brothers girlfriend has been having episodes at least 20 times a day and it's nothing I've ever seen before and I don't know what to think. She knows when it's going to happen so whatever she's doing she'll sit down so she doesn't fall and get hurt. Once the episode starts her eyes flutter rapidly and her eyes roll back in her head. She will start jerking her head back and forth rapidly and sometimes her head even falls back and she blacks out for a few seconds. She comes to after an episode usually lasting from 10-30+ seconds. When she regains consciousness she is fully aware of her surroundings and is not confused. Some or more violent than others bit regardless I don't know what to think of this. If any of you have suggestions as to what it is let me know.