Rachelle Bond, 41, pleaded guilty in February to charges including being an accessory after the fact to her daughter's murder.
Her former boyfriend Michael McCarthy was found guilty of second-degree murder and sentenced to life in prison last month
for the murder of the toddler. He will be eligible for parole in 20 years.
"The sentencing today just completes the circle of injustice," McCarthy's attorney Jonathan Shapiro told CNN in a telephone interview Wednesday.
"She got away with murder by making a deal with the prosecution to testify against Mr. McCarthy in return for her freedom. The jury needed someone to pay for this terrible crime. If it couldn't be Rachelle, then it had to be Michael."
Bond was in jail awaiting her own trial when she agreed to testify against McCarthy.
She was also sentenced to two years' probation for theft of over $250 by false pretense and for accepting government benefits meant for Bella after her death. Her probation will include a full psychiatric evaluation and rehabilitation for substance abuse.
Prosecutor: Agreements not entered into lightly
"We don't enter into these agreements lightly or capriciously or frivolously," Suffolk County District Attorney Daniel Conley said during a news conference Wednesday.
"We could not prosecute Michael McCarthy, and we would not have been able to hold him accountable without the truthful testimony of Rachelle Bond."
Bond served nearly two years in jail and will enter a rehabilitation facility for substance abuse upon her release from South Bay Corrections Center in Boston on Friday, her attorney Janice Bassil said in court.
"She is scared about her future," Bassil said. "She has a future without her child, and regardless of what people think of her involvement or not, she grieves the loss of that child every single day."
Bond's sentencing caps a saga that began in June 2015 when a jogger found an unidentified girl's partially decomposed body in a trash bag along Deer Island near Boston. Authorities launched an extensive effort to identify the girl, known as "Baby Doe," and commissioned an artist to draw a composite image of her that was widely shared.
A break in the case
The case broke open in September 2015, after Rachelle Bond admitted to a friend that her daughter Bella was dead, and that the girl had not been taken away from the Department of Children and Families, as she had told others, including the child's father. The friend recognized Baby Doe as Bella Bond and notified police. The tip led to the arrest of McCarthy and Bond.
Prosecutors relied heavily on Bond's testimony during McCarthy's trial. They claimed that McCarthy had called Bella a "demon,"
killed her and dumped a trash bag with the child's body into the water near Deer Island.
During closing statements, prosecutors said the devastating world of heroin addiction
had subsumed the lives of McCarthy, Rachelle Bond and those around them. Bond's attorney claimed it's a world that her client will try to leave behind.
"Once she completes an in-patient program, she will be in further step-down programs and eventually reach a point where I hope she will lead an independent life free of drugs and substance abuse," Bassil said.
In addition to attending rehab for substance abuse, Bond is also barred from residing with anyone who uses illegal substances, Suffolk County Assistant District Attorney David Deakin said in court.