I feel for you, hon. I am a huge fan of dogs (and a fan of huge dogs, I have mostly mastiffs). I once adopted an American Bulldog who had been a stray on the streets of Brooklyn. Brought him to my northern NY home in the mountains and he thought he'd gone to heaven.
Had him for nearly a year, then he started having seizures at around age 3. Vet said the same thing after the first one - it may never happen again. But it did. After awhile, he was having one every 6-8 weeks. Vet still said that as long as A) they don't last more than about 3 minutes and B) he doesn't start having them more frequently, like 1x/month, we shouldn't put him on any meds because of the possible long term effects. So we just dealt with it, and when it would happen, we moved things away from him & kept the other dogs away so no one got hurt.
But then one night just as I was getting into bed, Buster got up & left the room. I had a bad feeling about it, so I followed. He went to the living room & started seizing. After just over 1 minute, he started coming out of it... but then immediately went into another one. Had my husband get the vet on the phone, while I watched Buster & took mental notes. Vet wanted to see him right away, but there was no way we would be able to get him into the car- 130 pounds of flailing dog. She wanted us to try giving Valium, then maybe we could get him to her - but we didn't have that on hand.
By the time the vet went to her office to get supplies and then came to our house (this took over an hour, because we live in another town), Buster had already had about 9-10 seizures, one on top of the other. And he was SO hot. I kept covering him in towels soaked in cool water, but it didn't help nearly enough.
Vet got him sedated, then we took him to her office. Middle of the night now. By the time we left, she told us that his temp seemed to be coming back to normal quite rapidly, which she said was a very good sign - maybe there wouldn't be any brain damage. All we could do is leave him there and check on him in the morning.
The sound of the vet's voice the next morning will be forever etched into my mind. "Buster died," was all I heard. This was three years ago, and yet I'm still getting teary-eyed writing this now. Buster was absolutely the coolest dog with so much personality, and I will always miss him.
I know that this story probably didn't have the ending you wanted to hear... but there is a point to it. Please don't let your vet talk you out of putting your dog on meds for the seizures. Yes, there may be long term effects. But at least there will be a long term. I will never forgive myself for not doing this with Buster. Of course you want to wait to see if your dog has more than one... but when Buster started having them every 6-8 weeks, something should have been done.
Also, if you do not think you could get your dog into your car during a seizure, keep some valium on hand so you can get her under control & get her to the vet's office if needed. And third, get the cold, damp towels on her right away. I will always wonder if I had gotten them on Buster sooner, would it have made any difference? I was over-exhausted and not thinking clearly at the time, and he was probably 10-15 minutes into his series of seizures before we started working on his temp.
I wish the best for you and your fur baby. Please let us know how she's doing. Dogs are so wonderful, aren't they?