Her first and only appearance thus far was in Venus #18, February 1949. When she’d learned human beings had accidently killed her father with their atomic testing, she took the name Diana Seacrest and built homes as the owner of Seacrest Realty. She planned to bring great tidal waves to destroy the homes and kill the human beings who bought them.
Venus, in a mortal form, bought one of the homes and confronted her. In the battle that ensued, Neptunia was apparently killed when she was distracted and lost control of the storm she’d summoned.