That relies on a belief that good and evil are equals and that good isn't inherently a more mature state than evil. When good men go bad, they still believe they're good men. When bad men go good, they no longer believe they're bad men. In both cases, the person who is changing wants to be good. In real life the most famously selfish and evil people (republicans, tumblr, most tripfags) appear to lack empathy and self awareness enough to realize how shitty they are, and that is a characteristic of extremely young children. It can only be called immaturity.
So it's not a matter of if she can reform. She's evil to get attention, which shows she has an emotional connection to other people, however slight. So the potential is always there IF she chooses to grow up.
On the other hand, Wander becoming evil would require corrupting his values, so that he does evil for a greater good that may or may not exist. He's good, and nothing can just make him stop being good in his own eyes. You can't go backwards on maturity.