Michelle Heidbrick was killed in September, while crossing the street. She was pregnant, and her unborn child also died.
Rosalinda Vaca served little more than five months in jail before she was released on probation on Monday.
After pleading guilty to the most serious charge against her: failing to report a crash involving a death.
While Heidbrick's family was aware of the plea deal, they say they are not happy about it.
"I feel like the justice system failed Michelle. I feel like it continues to fail people every day," sister Nicole Heidbrick said.
Nicole Heidbrick said the baby boy her sister carried would have been born on January 28.
Heidbrick's pregnancy was at the 22-week mark, and she leaves behind a teenage son.
"She was a person. She was loved. She loved back. She had a full life ahead of her," she said. "I mean she struck and killed my sister and her unborn child and got a slap on the wrist."
The 36-year-old was hit and killed while crossing the street near Grand Avenue and Jackson Street in Waukegan around 9:30 p.m. on Sept. 21.
She was crossing the street with her fiancé.
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Surveillance video from a nearby gas station later captured Vaca's parked car while emergency vehicles responded to the crash.
Vaca turned herself in three days later. She remained imprisoned until her plea deal agreement.
A victim advocate with the Lake County State's Attorney's Office broke the news to Heidbrick's family.
In a statement today Vaca's attorney said in part: "Rosa made a statement in allocution expressing her deepest sorrow and remorse to Michelle Heidbrick's family. In this case, there are no winners and losers. Each family has been deeply impacted."
In addition to time served, Vaca will remain on probation for three years.
The Lake County State's Attorney's Office said in a statement: "We evaluate every case individually and consider all the facts.
In this case, we did not reduce the charges at all. This defendant pled guilty to the highest count charged. For the charge she pleaded guilty to, we typically see sentences ranging anywhere from probation to prison, depending on the specific circumstances of the case.
This defendant was sentenced to three years of probation following a period of six months in jail. It is important to note that if Ms. Vaca violates the terms of her probation, she can still be sentenced to prison."