“I thought I read that there was no way to determine that after death.”
There isn’t. Not unless she had a pacemaker or other device implanted that could be interrogated after death. No way. This is just a conjectured cause of death.
However, the media will eat this up and chastise those who conjectured anything different. I would be very embarrassed to call myself a journalist or reporter if I conducted myself the way so may of them do.