Gloria was a victim of Norman Bates.
While Gloria made out with the young Bates in her car outside of his and his mother's motel, Bates suddenly left to give his mother her 2:00 medication. After an apparent argument with his mother, Norman returned to the car and strangled her.
Gloria getting strangled by Norman Bates
Taking her to a nearby swamp, Norman dumped Gloria and the car into the river, drowning her.