Officers responded to a call of a "woman screaming" around 1am on Saturday to find Dr Harwick below a third-story balcony. She died from injuries "consistent with a fall", according to police.
An ex-boyfriend, Gareth Pursehouse, 41, was arrested the same day and booked into Los Angeles County Jail on 16 February, according to jail records. His bail is set at $2m pending a court appearance.
Her roommate told police that he jumped over a wall to get to a neighbour's house to call for help when he heard Dr Harwick being assaulted inside the home.
Police said they found signs of forced entry and evidence of the suspect leaving the scene of the killing.
"The investigation revealed possible evidence of a struggle in the upstairs as well as forced entry to the residence", according to a Los Angeles Police Department statement. "A canvass of the area located further evidence of an intruder ... entering the property and leaving after the murder."
The FBI's Fugitive Task Force arrested Mr Pursehouse on Saturday afternoon. and police said Dr Harwick had previously filed a restraining order against the 41-year-old suspect but it had expired. They had seen each other as recently as two weeks ago, police said.
Mr Carey, host of The Price Is Right, was engaged to Dr Harwick in February 2018. The couple ended their relationship later that year.
Dr Harwick, who practised marriage and family therapy in the Los Angeles area, wrote The New Sex Bible for Women in 2014. She received her Bachelors of Arts in Psychology from California Polytechnic University and a Masters of Arts in Clinical Psychology from Pepperdine University. She also graduated from the Institute for Advanced Study of Human Sexuality with a Doctorate of Human Sexuality.