I can relate to the fear you experienced. My dog Rudy, now gone, began having seizures just after he turned 1 year old. He was diagnosed with epilepsy and prescribed phenobarbitol (sp?). We never put him on it due to side effects we had read about. His seizures were sporadic but I made an entry in a notebook everytime he had one to see if there was some sort of pattern. I still have that notebook.
His came on suddenly, lasted a minute or two most times, and then he was fine. I would sit on the floor behind him and hold him. I stayed away from his mouth in case he got aggressive, but he never did.
He learned quickly to come find me when he felt one coming on, it was amazing. I would immediately sit on the floor - he knew I was there during the episode. I also hated to leave him for long periods of time, afraid he would seize without me there, fortunately my roomie was here alot when I was at work.
If your dog continues to have them,(I certainly hope she doesn't) I do hope you find the reason and maybe there is a remedy to help your dog.
Be strong for your girl, she will feel it.
A dog is the only thing on earth that loves you more than he loves himself.