Darn, I was really hoping she would go ahead and go with you soon. It would show a lot of maturity. I tend to think (speculate is more like it) that BiPolar (BP) kids still have periods of stability between extremem mood cycling even if they aren't on medds. It sounds to me like maybe she hit a period of stability. I might have missed it if you said this, but if she hasn't been taking her medications, now would also be a good time to try to get her back on them. Although, she might say that everything is fine now so she doesn't need them.
The problrm of course, is that the instability will come back without proper preventions in place. I'm glad you got to see her though. Maybe the next time she mentions turning herself in, you could say something about doing it asap to get it over with and to keep her from changing her mind. I don't know that I'd want all charges dropped either, but certainly, she should get a much lighter sentence if she steps up to the plate and shows that she is working and trying to be responsible than if she stays on the run.