So the parents wanted their kid put in jail to detox even though they knew it was not the best place but they felt like they had no options. Now they are suing? She went in weighing 80 lbs that's a red flag right there, sounds like she was most of the way there BEFORE going to jail.
Yes it is sad, but corrections is not a replacement for medical care.
If you are doing hard drugs, take responsibility for the outcome, including death. No way to sugarcoat it.