You don't provide enough information for anyone to answer your question. Why is your granddaughter in PRTF (Psychiatric Residential Treatment Center)? What involvement do her parents have with her? What are her doctors' recommendations? What is her condition? What is the prognosis? What do her other providers recommend? Is there an ongoing court case pending? If so, what has the judge previously ordered? Does she have an attorney? Do you have an attorney?
The answers to all these questions are important in deciding how, when, and under what circumstances she can be released from PRTF and what can be your involvement.
This response does not constitute legal advice and does not create an attorney-client relationship. I am licensed to practice only in Kansas. Seek legal advice from an attorney in your state or the state in which your legal claim exists.