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.
"He has a new girlfriend now -- she's very nice and cares for Leah well," Shawn said.
"Most of Amber's problems revolved around Gary, so it's a hot issue. He can keep Leah away from Amber, and in the past when that's happened, it triggers Amber in a bad way. Her demeanor has changed, so that will help."
Amber and Gary have a 4-year-old daughter together, Leah, who Shawn says Amber only got to see a few times while locked up, so the reunion between the two will be emotional.
Once she's released, Amber's brother says she plans to stay clean and has no interest in the limelight again.
"She wants none of that life anymore," he said.
"She's grown up far more than I thought she would. When I talk to her, she's changed."
For the full interview with Amber's brother, pick up the latest issue of OK! magazine, on newsstands Thursday.