I wouldn't knock someone immersing himself in his religious community in lieu of hospice if he had a bad prognosis.
But it starts getting weird that his condition was kept so quiet, and his death, too. That his widow is expected to teach a class is a cruel expectation. When you review the warning signs of a cult, these abusive work regimens are often part of that.
I don't know anything about Christian Scientists, but that doesn't matter. Cult-like pockets can exist within any religion, just some are more structured for it than others. The element needed is a charismatic central figure and your friend's widow is very vulnerable to whoever that is right now.
There might not be anything you can do about it. If it's a cult and you try to help her, you'll be cut off from contact with her.