Bright-eyed and grinning, Amber Portwood looked like a new woman as she left prison after serving a 17-month sentence on Monday morning. Portwood told reporters that she'd found the strength to stay clean inside prison walls, after initially struggling with the terms of her drug program. And now, Breaking Celebrity News has learned, Portwood's brother Shawn Portwood is revealing just how much of a transformation he's seen in his sister since she surrendered herself to the mercy of the court.

The former Teen Mom "has had a lot of negative press in the past, which has portrayed her as a very hateful individual," her brother wrote in an emotional blog post earlier this year. "And she was for a while. She did not know how to control her anger or even shut up when she needed to. But now I am happy to say that I absolutely believe that it is all behind her now."

Amber had asked an Indiana judge to throw her in jail for five years to deal with her addiction issues, and the judge complied.

"After Amber was sent to prison, she had a lot to think about and a lot to change about herself," Shawn explains. "…In one of her first letters to each other, Amber wrote and said, 'I just hope you guys understand that I chose prison to help me, and to pretty much save me from myself.' She told me that she cried often …"

But she chose that route, he says, "because she did not have the strength to survive on her own and stay clean." Portwood had struggled through a stint in rehab, as well as a hospitalization following a suicide attempt.