Mitchell, 55, was released from the Bedford Hills Correctional Facility in Westchester County, New York, to community supervision, according to the Department of Corrections. She'll be supervised in Franklin County until June 2022.
Mitchell was convicted for providing material support to Clinton Correctional Facility prisoners Richard Matt and David Sweat in a dramatic case that eventually became the plot for the 2018 Showtime miniseries "Escape at Dannemora."
Mitchell was charged with promoting prison contraband in the first degree -- a felony -- and criminal facilitation in the fourth degree -- a misdemeanor -- and sentenced to to between 2 1/3 and 8 years in September 2015.
She admitted to charges of promoting prison contraband and was also ordered to pay $80,000 in restitution for damages incurred during the escape.
The story gained national attention as authorities spent 22 days searching for the escaped upstate New York killers.
The June 2015 manhunt came to an end when Matt was shot and killed by authorities and Sweat was shot and apprehended.
It was later revealed that the inmates had seduced Mitchell, who worked as a prison tailor, as a part of an elaborate scheme.
In 2015, Mitchell allegedly agreed to flee with Sweat and Matt and helped collect items including guns, ammunition, camping gear and a compass, according to a report from the New York inspector general.
"She professed her love for Sweat in notes she secretly sent him," the report said, but she also allegedly "engaged in numerous sexual encounters with Matt in the tailor shop."
Mitchell allegedly smuggled hacksaw blades, chisels and other tools into the prison in frozen hamburger meat, which a guard later gave to the inmates. She also allegedly bought six hacksaw blades and gave them directly to Matt, according to the inspector general report.
The inmates used power tools to cut through the back of their cells, broke through a brick wall, cut into a steam pipe and then slithered through it, finally emerging outside the prison walls through a manhole, officials said.
They had arranged hoodies and other clothing in their sheets to make it appear as if they were in their beds, officials said, leaving behind a note that read, "Have a nice day."
Mitchell had planned to meet the inmates on the outskirts of the prison with a getaway car, but she got cold feet and didn't show, forcing the escapees to regroup.
At her sentencing in 2015, Mitchell told the judge, "If I could take it all back I would."
"This is by far the worst mistake I have ever made in my life. I live with regret every day and will for the rest of my life," Mitchell said.
"Escape at Dannemora" -- named after the town where Clinton Correctional Facility is located -- was directed by Ben Stiller and won several awards. Patricia Arquette, who played Mitchell, won a Golden Globe, Screen Actors Guild award and Critics' Choice Television award for the role. Stiller won a Director's Guild award for best miniseries or TV film. The miniseries was also nominated for seven Emmy awards.