True enough. You also don't have to save someone who is drowning.
I don't think we have a right to use force of law to compel her to give her marrow. I do think that her decision has consequences, one of which is that she if publicly scorned.
She is not entitled to be free of scorn, either.
Exactly! In a free society, people are entitled to make all sorts of selfish decisions. But everyone around them is also free to judge those decisions. Some decisions are deserving of scorn.