The 35-year-old woman is accused of lying to investigators about what happened the day Walker killed Sgt. Derek Johnson and could spend up to 30 years in prison if convicted on both counts.
Walker, 34, who ultimately turned the gun on Vaillancourt his girlfriend at the time and then himself in a failed suicide bid, was sentenced earlier this month to spend the rest of his life in prison for killing the officer.
But prosecutor Vince Meister said after Tuesday's hearing that Walker's conviction has "no impact at all" on Vaillancourt's case.
According to court documents, Johnson was in a marked Draper City police vehicle about 6 a.m. on Sept. 1, when he noticed Walker standing outside of his stopped Volvo near 13200 S. Fort St.
Walker had stopped the car because he ran out of gas and the passenger-side front tire had gone flat from driving over a curb, a stop sign, a large rock and then through a fence at 13800 S. 933 East.
He kept driving a few blocks to the area of 13200 South before he encountered Johnson.
When the officer pulled up near the Volvo to see if he could help, Walker shot Johnson through the open front passenger-side window of the police car.
The bullet hit Johnson in the chest. He tried to drive northbound to safety, but Walker, who was allegedly under the influence of methamphetamine at the time, fired at least three more shots, which struck Johnson's vehicle.
Johnson, 32, died a short time later.
After Vaillancourt's September hearing, a judge will determine if there is enough evidence to order her to stand trial.
Vaillancourt, meanwhile, is at the Salt Lake County Jail, where she is completing a drug treatment program.
Her attorneys said Tuesday she was doing "much better" than she had been.