She was cremated, unheard of for a good Catholic in that time.
The details are a little hazy.
My guess is they let the family know that there would always be questions and an endless series of exhumations and autopsies to resolve those questions, and that poor dear Mary Jo would never rest in peace, unless she was cremated.
Or perhaps there were subtle or not so subtle threats, or perhaps there were other inducements?
Mere mortals like you or I will never know.