My little mixed dog, 11 lbs, started having seizures daily sometimes 2 or more. Vet recommened 1/2 phenobarbital tablet twice a day. there was no change for the first week, now she is doing good. Little dog may have seizure once in a while but not as often or as long. She seems to be happiers. Only side effect is she like to eat, so now we have to be carful not to give snacks everytime she wants one.
Get second opinion.
You have a beautiful Sheltie.