I know of someone who had a possible seizure at the supper table? She was sitting there after supper laughing and then all of a sudden she was on the floor twitching and glassy eyed? It only lasted a few seconds and then she got back up and sat at the table. She had her parents checked her blood sugar and it was 139 at 6:00 at night. She said she felt kind of weak. Could she have had a diabetic seizure?

That blood sugar level would have been totally appropriate for that time of day. In this context, it doesn't SOUND like it would have been. Usually a low blood sugar (50's or below usually) would be a more typical level for this sort of response.

That person should probably be seen by a doctor to simply rule out other possible issues as well.