Former Teen Mom star Amber Portwood's stint in prison was cut drastically short thanks to good behavior and her brother says she's a changed woman with big plans for the future.

Amber, 23, is slated for release from Indiana's Rockville Correctional Facility on Nov. 6, four years early, and her brother Shawn Portwood tells OK! magazine that she completed drug rehab and got her G.E.D. while serving her time.

"She's really grown and matured -- she completed her drug rehab in prison, she got her G.E.D., she completed parenting classes and she became the administrator of the CLIFF program, which helps inmates get sober," Shawn told the magazine.

"She did so well in cleaning herself up, that she spent most of her jail time helping other girls get clean."

Before entering prison -- voluntarily, because the mother of one didn't think she could sober up on her own -- she had an on-again-off-again relationship with baby daddy Gary Shirley, but her brother says there's little chance of the romance rekindling once she's released.