My Frasier had vestibular syndrome and he also had seizures. I always felt that the two were related, though it's not supposed to work that way. His seizures were pretty bad from the get-go, with his post ictal stage lasting for several hours with him snoring away in a very very deep sleep. He took phenobarb that did control his seizures pretty well, thankfully. He'd be laying down and the next thing I'd know, my female hounds would run to him and I'd know it was a seizure, he's look control of his bladder and have his seizure for a minute or so and then get up and stumble around for a bit until he lay down and fell asleep in his post ictal state.
He passed young, but from something totally unrelated to either seizures or vestibular.
I have a blind dog who has vestibular and has it pretty bad. He's had 3 vestibular incidents and each one has taken him longer to get over. The first one was a few days to get over and the last one took months for him to get over. I worry that he won't get over the next one if there is one.
Good luck with Athena, now is the time to find her a good vet for her seizures, and I, personally, would ask for something to control her seizures at this point.