Well, she predicted it herself, so I guess I shouldn't be surprised that others did as well.
The book is filled with evidence. A former MI5 agent revealed an MI5 document that contained a detailed plan to murder a Serbian politician by blinding his driver in a tunnel with a bright light and thus causing an accident. Several witnesses inside that tunnel in Paris said they saw a bright flash just before the Mercedes crashed. Diana also received a death threat for speaking out against land mines (a friend of hers was with her when she got the call). It's really not rocket science. She was no longer a royal, she knew way too much and she wasn't shy about leaking their dirt to the press (and rightfully so). Heck, Prince Harry said in an interview he'll never stop wondering what happened inside that tunnel. Doesn't sound like he believes the official BS, either. I can't imagine that anyone honestly thinks the Royal Family would never murder anyone who they think is a threat to the monarchy.