8 year old had abnormal EEG with occipital spikes, &. Never had a seizure, should she be on medication? How likely is it that she would have a seizure

Hard to say. Without doing a complete history & physical and reviewing the actual EEG report, it is hard to comment on what course to take. You have not stated why the EEG was obtained or what other issues are present.Some childhood conditions are outgrown over time and there is a trend to avoid medications unless necessary.
Yes. Risk factors to have a recurrence after the first unprovoked seizure include abnormal eeg, seizure occurred during sleep, and todd's paresis.