Officials said she would be released within one week from Albion state prison where she is currently being held.
"She's been served [with the decision] this morning and granted release," state parole board spokesman Thomas Grant said.
The three-member parole panel, which interviewed Fisher Tuesday, voted 2-1 to free her, according to Grant. He said the board has ordered her release within a week from the western New York prison where she is being confined.
She could be let out sooner, Grant said.
Fisher shot Mary Jo Buttafuoco, her lover's wife, in the head at her home on New York's Long Island in 1992. The teen was sentenced to five to 15 years in prison for first-degree assault.
A judge last month agreed to give her a shorter prison sentence, making her eligible for release. During a court appearance, Fisher took responsibility for the shooting and apologized to Mrs. Buttafuoco.
"What happened to you it wasn't your husband's fault ... it wasn't my father's fault. It was my fault and I'm sorry," she said.
Mrs. Buttafuoco, whose husband, Joey, served six months in jail for statutory rape after the affair, said her faith in God allowed her to forgive the woman who seriously wounded her. The two corresponded for several months.
The Buttafuocos now live in Los Angeles, where Joey Buttafuoco has been a cable television talk show host. The case inspired several television movies.