Welcome to the board, Peter and Sophie!
Was the vet able to observe the ear twitch while Sophie was being examined? If not, it might be useful to try to get a video clip of it, although that might be difficult given the timing of the twitches. But I think I'd attempt it if there's no improvement on the Zonisamide. A canine neurologist might be able to tell you from a video if the twitch could be seizure related.
It could just be that she was developing an ear infection and the cleaning and Otomax knocked it back enough that the vet couldn't detect it--that might also explain the slightly elevated WBC.
She twitches in both ears, but not both at the same time?