I have been on parole for over two years. My sentence is scheduled to end in 2011. I got a misdemeanor DUI on 10/21. Is it up to my PO's discretion to send me to jail or is she simply obligated to do so?

Depending on what your original conviction was for your original sentencing judge could send you back. It's not up to the PO, but to the Judge. You already are in violation having consumed alcohol and driving drunk.