Any reason a hospital would absolutely refuse to give a young person plasma to try & save her ?
This is a very sad story, for the young woman involved, of course, but also for the family and friends who feel that they were mistreated. However, there are several good reasons why a hospital might refuse to treat a particular patient with convalescent plasma.
The plasma has antibodies that can neutralize the virus
before it damages the body, so if the disease had progressed very quickly in her, it might have been too late for the plasma to have any effect. The virus might already have caused so much damage to her heart or lungs or kidney, for example, and it would be much more important at that point to use treatments that treat that damage. In fact, the very first tests of convalescent plasma found that when it was given to the sickest patients, it made them worse. (You might think of this like someone throwing a lit match towards a house. You say "Blow out the match!" to prevent a fire. But once the house catches on fire, you don't say "Let's look for that match and blow it out! That'll stop the fire!" No, at that point you need to address the burning house.)
It's also possible that she had some condition that would make the plasma inappropriate for her. For example, one risk of giving the plasma is that it can cause dangerous blood clotting in the patient. If she had a condition that made blood clotting a problem, then giving plasma could worsen her condition.
Covid patients have a variety of different symptoms, and for her symptoms, they might have felt that other treatments would better help her.
I don't have medical training or experience, but these are a few things that come to mind from reading a little on the topic. Maybe someone with medical knowledge can comment.