The prosecutor has great discretion in the punishment requested, especially in juvenile matters, and the court has even greater latitude in sentencing. The one factor that will make the difference in outcome will be the abilities and efforts of defense counsel. If the family can afford it, hire the best. If not, apply for the services of the public defender and offer full cooperation.
Best wishes for a favorable outcome, and please remember to designate a best answer.
This answer is offered as a public service for general information only and may not be relied upon as legal advice.
I agree with Ms. Sinclair's response. Another factor to consider is that Juvenile Courts are designed to promote reform for troubled youth as opposed to simply punishment. This doesn't mean that if convicted she won't face punishment, but it means that the court should consider whether she needs help, such as treatment for trauma or other conditions, and it should provide for that help if it determines that she needs it.
You also stated that your sister is on medications. If she suffers from mental health problems, the judge should consider whether that factor contributed to her behavior. Perhaps she needs treatment more than punishment?
I'm getting a bit ahead of myself. Like Ms. Sinclair said, hire the best criminal defense lawyer possible. Find one who will fight aggressively for your sister, one who will thoroughly review the evidence and the process used to collect the evidence, whether the police followed all of the rules or if some evidence can be suppressed; and even then, a lawyer who will ensure that the state can prove its case against your sister. If all else fails and she either accepts a plea offer or is found guilty, ensure that you hire a lawyer who will spend the time to learn of her circumstances (including health issues), and who will argue to the court for a fair sentence that provides for her to receive any help that she needs as opposed to merely punishing her. Good luck!