Exactly this. The issue is not that she lacks capacity, but that she is making judgements and decisions about her condition which are not based on the information her doctors are giving her but are, understandably, based on the opinions of the people she loves and trusts best in the world, through whom all her information is filtered and who are , in their desperation, perhaps not facing up to the reality of her situation.
It is something we have seen before , the difference in this case is that ST is a young person who is expressing her own opinions and the Courts are quite rightly spending time taking her opinions under consideration. It was different when the opinions in previous cases were mediated by the adult careers about their incapacitated children, this is a young but technically adult patient expressing her own views, and it makes the concept of capacity much harder to judge, because capacity re making a decision is not based on the appropriateness of the decision, but on the ability of the patient to take into account all the nuances and information available. And in this case the judge has ruled that ST has not understood the situation regarding any additional treatments.