"Since there reportedly are no risks, this is nasty of the sister. There have been cases of strangers doing more for those in need of organ donations."
There are indeed risks, as there are to any sugery, especially those that require anesthesia. Seriously, you have to get into the bone somehow, they don't just magic the marrow out into a jar by telekinesis.
I think its interesting that most people jumped to the conclusion that the sister is a spiteful hateful person, simply on the report of the husband's wife, who seems a little off-kilter herself. (How many of us need to get arrested when we fly off handle?)
I can think of a good many reasons why someone would be unwilling or perhaps uneligible to undergo this procedure.
We are operating on a serious lack of information here, and what we have is very one-sided.
I see your point.