After a first unprovoked seizure, antiepileptic treatment is started when the recurrence risk is high - and an EEG with epileptiform abnormalities (spike waves here) and a nocturnal seizure are both high-risk features. So start treatment now (lamotrigine is reasonable in a young woman, avoiding valproate's teratogenicity). Repeating the EEG or waiting for a recurrence ignores the already-abnormal EEG; an antidepressant does not treat epilepsy.