I have to agree with Izzy77523. I don't believe she ever made it to the prison. I lived in Huntsville and I'm not far from the area now. Just going by the locations people claim they last saw her, I highly doubt she made it to the prison.
If she had made it to the prison there probably would have been several witnesses.
It's my guess between the time she was last seen and her body found that she was never far from the I45.