My friend has a son who is diagnosed bipolar.
They put him on among other meds, Depakote, which has long been known to be used with seizures...though he has never had a seizure.
So I think your answer is that she does not have to have seizures (epilepsy is a blanket term which I was told meant seizures of unknown origin)to be taking a med that is normally for seizures.
She may have been prescribed the med to normalize brain functions.
Wish you luck,