The Constitution provides protection for all citizens, including Mrs. Schiavo. Therefore, she has a right to refuse medical treatment, food, water, etc. She has a right to choose to live and a right to choose to refuse to live. She also has a right to exercise her rights immediately, not delayed by more interference from outsiders. Rights delayed are rights denied.
We also have courts to decide legal matters. Unfortunately, Mrs. Schiavo left things to the courts with little to go on...but many courts have done their best in making determinations based on a heck of a lot more information than the FReepers here. Have any FReepers watched the 4 hours of video? Few, I'm sure.