I just wish more people understood that to "fully support and love someone" doesn't also mean you have to agree with, accept, and encourage self destructive choices or behaviors. (Or in this case, self-destructive avoidance of lifesaving care.)
I think the mother should be allowed to be there in the hospital with Cassandra, if they both want that. I do think that supervision is still necessary, to make sure treatment isn't sabotaged, but I think keeping them apart with only brief twice weekly visits is just stoking the fires of resentment (mother's resentment, mostly). Better we should nurture this mother/ daughter bond, as they both face scary and difficult times. Lead by example, welcome the mother's care and presence for her daughter, show her what she can do, and how she can help nurture Cassandra. Help the mother feel needed, especially since she is so angry her decision making was usurped by the courts.
Sure, having hostile family members around on a hospital unit is no picnic for the staff-- but these are really the families that need us most to teach and lead by example. I'm sure there are some nurses that would want no part of caring for Cassandra if Mom was there all the time, and would avoid being assigned to her, but others would step up, and hopefully build a bridge of trust over time. Difficult families are always a challenge, but we owe it to them to try, and try again-- as long as there is no overt abuse of the staff, or sabotage of the medical and nursing care. Angry families mean we just have to work harder to understand each other. I've learned over many years that often "angry, critical, and resentful" = "very scared." Angry patients and families often feel out of control, anxious, and intimidated by medical care and experiences, if you look behind the anger.
(But often that's pie in the sky optimism-- because in the next breath, I can tell you that angry & resentful patients and families are the most draining and frustrating people to care for.)