Donella was last seen in Pasadena, California on December 18, 1979. Her husband, Leonard Coultas, said they had an argument and she ran out of the house angrily. She has never been heard from again. She left behind her purse, wallet, wedding ring and keys. Leonard stated she had only $50 and a credit card with her when she vanished, and the credit card was never used.

Donella's family believes she did not leave voluntarily and they think Leonard killed her. He stated their argument was violent and she hit him with a rock. He admitted he struck his wife in the head with a vase, breaking it and causing her to bleed from her nose and ears, but he denies that he murdered her or knows her whereabouts. Although the police considered him a suspect at the onset of the investigation, some evidence in the case was lost and Leonard has never been charged in Donella's case.

Leonard and Donella have a son who was two years old in 1979. She was working as an executive secretary at the time of her disappearance. Her mother died in 2012. Authorities believe Donella vanished under suspicious circumstances. Few details are available in her case, but foul play is suspected.