I don't know if C. Ann is still reading this board, as I am sure she is much pre-occupied at the moment.
There is certainly something very strange about this and she should be very aggressive in persuing the issue with the police/medical examiners office/coroner, etc.
She should begin by calling her local police and asking if she can come down to talk with them at a time that is convenient. When she does, she should ask THEM (her local police) to make some calls for her after she explained what happened and what her brother in law did.
HOWEVER, C. Ann must be prepared to answer some questions that she will find very uncomfortable (as they have confused me as well). Her local police will ask her:
Did you not find it strange that you had not spoken to your sister in TWO YEARS?
If you were told that she was in the hospital, you didn't visit her in the hospital for the TWO YEARS she was there?
You said you got alot of advice from folks on a Disney board, you mean you have been to Disney a number of times in the past two years but have yet to visit your sister who was hit by a train?
They WILL ask these questions because the police have to decide who is making things up, the brother in law or the sister and if the answers to these questions aren't good the police are likely to ignore C. Ann.
Good luck.