IMO, she is not able to be rehabilitated. She was receiving therapy more often than the average troubled teenager, she was prescribed medication, and she had grandparents that supported her, yet she still willfully and purposefully chose this path. There are many kids who had it worse than her who did not commit this level of premeditated murder. They may have committed minor crimes, but nothing in this level. She is a sociopath. Her influences in life have little to do with it, IMO. And she had all the help she needed. She still chose to become a cold blooded killer. There's no rehab for that.
Once again, this is all just my opinion.