Under the Weather Puppy

Lucy gave us quite a scare this morning at 4:30 AM, when she suddenly suffered a massive and violent seizure. She started foaming at the mouth and convulsing, and rolled over on her right side. I ran to her and held her until the seizure subsided. She was uncharacteristically antsy last night at bedtime, and kept pacing in the hall.
It was all over in under ten minutes, she had trouble walking at first, and we wondered if she had a stroke, but then she started walking around as if nothing had happened, before laying down and going into a sound sleep.
I called from work at 7:15, and Mrs C said she was still sleeping peacefully, snoring away, but Sally and Ethel had both come in and lay down, snuggling up next to her, and licking Lucy.
I called the vet at 9 AM and got her in for a 4 PM appointment. At 3:30, as I was preparing to take her, she started having another, suffering several tremors, and I rushed her to the vets office, where they were able to witness this, less violent attack.
It could be anything, and they did her blood work, but within minutes she was fine again, and her happy little self. She's a senior dog, more than 12 years old, which translates into the 80s for an average human. I've been more worried about Ethel, who will be 13 in June, that Lucy had issues was something out of the blue. I know it is inevitable, but I hate thinking about it.
Lucy is my little black shadow that follows me around the house wherever I go.