Prison (or even local jail time) is a coarsening, soul-sucking existence. There is a reason why people don't want to go to there and use every legal remedy to fight to get out once they are sent. No sunlight, no grass, no sand and ocean breeze, no smell of a pine tree at Christmas, no quick trip to the mall for new shoes, no sitting on the porch watching sunrise. A world full of people who are in prison (for the most part) because they can't follow society's rules or because (like Casey) they see other people as not as real or important as themselves.
Casey is in this situation because she could not bear the restriction of having a child that her parents were willing to support, baby-sit, and essentially raise. She didn't have razor wire, guard towers, open toilets and cell block doors in mind when she envisioned la bella vita. Prison is serious punishment, and the best she can hope for is 30+ years. She will come out, if she ever leaves, middle-aged with no skills or education. Her parents would be old (if they live through the stress of Casey's imprisonment) and we can only imagine what kind of relationships she will have with her brother when this trial is 30 years in the past. The only hope she has is to change her inner life, which I can't see ever happening, although we can hope for miracles). And of course she has to live with the knowledge that she murdered Caylee, now that her bubble of denial has been pierced by the trial. Prison will be hell, wherever she serves her time.