Will a person with epilepsy sometimes have a normal eeg?

Yes. The first eeg is normal 50% of the time in someone with epilepsy. Three routine eegs result in a 90% sensitivity (finding abnormality consistent with epilepsy). 24 hour eegs may be even more sensitive. Not all people with epilepsy have abnormalities in between their seizures, but many do.
Yes . An epileptic may have a normal eeg. A normal person may have an abnormal eeg. It takes clinical judgment and experience to decide what to do medically.