Valérie Bacot, who shot her husband, Daniel Polette, in 2016, was convicted of murder and sentenced to four years, including three years suspended.
But she was released from the court of Saône-et-Loire, in eastern France, because she had already spent a year in pre-trial detention.
The verdict was greeted with thunderous applause from the courtroom and some of Ms Bacot’s friends and family broke down in tears.
Announcing the jury’s decision, Judge Céline Therme said the court recognized the “terror” Ms. Bacot had endured for years.
Prosecutors had told the court that the 40-year-old should not return to prison because she was “very clearly a victim” of her tyrannical husband.
Ms Bacot was only 12 when Polette, her mother’s boyfriend at the time, first raped her.
He was imprisoned after the initial rape but continued to abuse Ms. Bacot after her release, and she became pregnant at the age of 17.
Ms Bacot’s alcoholic mother threw her out of the house and she was forced to live with Polette, who then forced her into prostitution.
Ms Bacot, who confessed to shooting Polette, 61, and hiding her body in a forest with the help of two of her children, last month published a book about her experiences.
Her case has become a famous feminist cause in France at a time when more and more women are breaking the silence on sexual assault.
“I feel empty rather than relieved”
“I want to thank the court,” Ms Bacot said as she walked freely, looking frail.
“It’s a new fight now for all other women and all abuse,” she said, adding that she felt “empty” rather than relieved.
Eric Jallet, the public prosecutor, had declared earlier in court: “Valérie Bacot should not have taken the life of the person who terrorized her”.
But the judges should “confirm the transgression without incarcerating him again,” he said.
A visibly tired Ms Bacot had collapsed upon hearing the prosecutor’s request, prompting emergency personnel to intervene and the hearing to be suspended briefly.
More than 700,000 people have signed a petition demanding that Ms Bacot, who had risked life in prison, be exonerated.
She told the court how she felt trapped staying with her attacker. “I wanted to keep my child. I had no one. Where can I go? she said.
Polette grew increasingly violent, attacking her at one point with a hammer and forcing her to prostitute herself for truck drivers in the back of a van.
Polette threatened to kill her and the children if she left him, pointing a gun at her repeatedly. Ms. Bacot described her life as “extreme hell”.
When he started asking their 14-year-old daughter, Karline, about her burgeoning sexuality, Ms Bacot said she decided “this has to stop”.
In March 2016, after Polette ordered Ms Bacot to undergo further sexual humiliation by a client, she shot her husband with her own gun.
Ms Bacot said she wanted to make sure her daughter did not suffer the same fate as her.
An expert report ordered by the court revealed that she was “certain that she had to commit this act to protect her children”.
She hid the body in a forest but in October 2017 she was arrested and then released on bail.
Her lawyers, Janine Bonaggiunta and Nathalie Tomasini, previously defended Jacqueline Sauvage, a Frenchwoman sentenced to 10 years in prison for killing her abusive husband.
Ms. Sauvage obtained a presidential pardon in 2016 after becoming a symbol of the fight against violence against women.
Ms Tomasini said Friday’s verdict, while allowing Ms Bacot to free herself, was still too harsh.
“How can society seek redress from Valérie Bacot, when it has not been able to protect her? she said.
She listed a “chain of dysfunctions” that prevented the authorities from protecting Ms Bacot, including the fact that relatives had twice tried to alert the police, to no avail.
Violence against women has become a growing political issue in France, where cases of women murdered by their partners have repeatedly made headlines in recent years.
Hundreds of women demonstrated in Paris on Friday against what they called government inaction on the issue, carrying signs saying “silence is killing us.”