This is not legal advice. Under the facts as I see them, liability is a long shot. Certainly, someone of 17, almost 18, has more autonomy over her body than her parents. It is legal to belong to controlling religions. Arsenic is used in palliative care. Causation that no transfusion caused her death, esp. when she was dying, is farfetched. If the answer is questionable, the doubt goes to the defendant.
I know from civil rights in the States that jurors are now very sensitive to the overall impact of damage claims. Excessive damage claims have a societal impact. We pay in higher insurance premiums. From my viewpoint and reading of the law, case after case that met the criteria came before a jury. Juries go with an overall feel. They don't want mere negligence. Without aritculating it, they seem to holding people to a gross negligence standard.
Anyway, the Witnesses were dismissed as defendants, if I am correct. It means in the states that if everything alleged were proven, no liability would exist.
Adults are free to make wrong-head silly decisions affecting their autonomy. As much as I despise the Witnesses, I see no liability concerning anyone. This is a tragic case. The law does not correct every sadness or injustice. I disagreed with my JW father. IN fact, when he died I was ready to go to court so I could finish high school. Law has to be neutral. You can't pick your principles.
Losing a child must be utter hell. I feel like crying. She should have had a long life. Maybe fundraising for treatment of her cancer type would be a good way to invest time. This case has been hanging around for a while. Is something else going on?