The D.A.'s Office said McNeal was the victim's ex-girlfriend, and claims she and Napolski killed him at his Newport Beach home in 1994 to collect insurance money.
"The defendant had taken out a $1 million insurance policy on the victim, as well as made allowances in his will that she would receive hundreds of thousands of dollars in the event of this death, as well as to be able to live rent free in his homes," said Farrah Emami from the Orange County District Attorney's Office.
McNeal is accused of giving Naposki a key to McLaughlin's home, where he was shot.
McNeal pleaded guilty in 1996 for stealing nearly $500,000 from McLaughlin before and after his death. She was sentenced to one year in jail.
McNeal at the time denied that she or Naposki were involved in the shooting. On Wednesday, after she was put in a police squad car and led to jail, she maintained she wasn't guilty.
Naposki was arrested in Connecticut and will face extradition proceedings. McNeal was arrested in Orange County and is scheduled to be arraigned Friday. Emami said she didn't know if they had retained attorneys.
McLaughlin founded a company that developed a device that separates plasma from blood. He had an estimated $55 million fortune, according to court records.
The Associated Press contributed to this story.