Police have said the 50-year-old Coke and Alana dated briefly about 20 years ago. Coke was an investigator with the Sacramento branch of the Federal Public Defender's Office.
She vanished after leaving her Oakland home Aug. 4. Her body was found five days later.
Alana has denied harming Coke, and said the two planned to marry.
Alana has several prior convictions, including for robbery and involuntary manslaughter.