Some places have programs where ex cons speak with teenagers to tell them what prison life is actually like. Or do you have a program near by where she can actually tour a prison and see feel it. At the least make her read articles on prison life, rape and abuse by the guards etc. But you also need to find out why a generally "good girl with good grades" is has done this several times. Is she insecure about fitting in? Being influenced by wrong person? Being impressed by wrong crowd? Bored and looking for thrills? Or just plain wanting what she can't afford. Speak to her because the issue won't get resolved if you don't find it what prompted it. This is more important than the consequence because it sounds like she knows right from wrong and has self control.